LIGHT VALVE PROJECTOR WITH LASER-PHOSPHOR LIGHT CONVERTER

• US 20140240676A1
• Filed: 02/27/2013
• Published: 08/28/2014
• Est. Priority Date: 02/27/2013
• Status: Active Grant

• Current Assignee: Barco NV
• Original Assignee: Barco NV
• Inventors: Maes, Dirk L.A., Defever, Rik, Maximus, Bart Henri Johanna
• Granted Patent: US 9,170,475 B2
• Time in Patent Office: Days
• US Class Current: 353/20
• CPC Class Codes: G02B 2207/113 Fluorescence
• CPC Class Codes: G02B 30/25 using polarisation techniques
• CPC Class Codes: G02F 1/133614 using photoluminescence, e.g. phosphors illuminated by UV or blue light
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence
• CPC Class Codes: G02F 1/136281 having a transmissive semiconductor substrate
• CPC Class Codes: G03B 21/16 Cooling; Preventing overheating
• CPC Class Codes: G03B 21/2013 Plural 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: G03B 21/2073 Polarisers in the lamp house peculiar to electronic spatial light modulators H04N9/3197
• CPC Class Codes: G03B 21/208 Homogenising, shaping of the illumination light
• CPC Class Codes: H01S 5/0087 for illuminating phosphorescent or fluorescent materials, e.g. using optical arrangements specifically adapted for guiding or shaping laser beams illuminating these materials
• CPC Class Codes: H04N 9/3158 for controlling the spectrum

Abstract

A method and system are presented directed to a light valve projector with a laser-phosphor light converter. The phosphor converter converts excitation light in order to provide light to a light valve projector. The phosphor converter reduces the étendue of laser-phosphor light sources using a light pipe integrator system. The light pipe integrator system includes a light pipe integrator configured to mix the excitation light and reduce the spot size of excitation light entering the system from, e.g., a laser array. The excitation light is imaged onto a phosphor as it exits the light pipe integrator. The phosphor emits fluorescent light, in response to being illuminated by the excitation light, that enters the light pipe integrator. The light pipe integrator reduces the emission angles of the fluorescent light while maintaining the étendue of the fluorescent light. The system and method may include a reflective polarizer to polarize the fluorescent light.

Claims

1. A light valve projector comprising:

a light valve device;

a source of polarized excitation light;

a phosphor converter receiving the excitation light;

the phosphor converter comprising;

a phosphor material located on the surface of a reflector and a light pipe integrator system,

the phosphor material, when irradiated by the excitation light, emitting fluorescent light having a different spectrum than a spectrum of the excitation light;

a light pipe integrator system comprising a light pipe integrator;

the light pipe integrator having a first surface through which the excitation light enters the light pipe integrator and a second surface through which the excitation light exits the light pipe integrator;

the light pipe integrator system positioned relative to the source and the phosphor material such that;

when the source outputs excitation light, the first surface of the light pipe integrator receives the excitation light;

when excitation light exits the second surface of the light pipe integrator, the excitation light is imaged onto the phosphor material;

the light pipe system positioned such that, when the phosphor material emits fluorescent light, the second surface of the light pipe integrator is positioned to receives a majority of the fluorescent light and the fluorescent light is transmitted to the first surface of the light pipe integrator; and

the light valve device positioned such that, when the fluorescent light exits the first surface of the light pipe integrator, the fluorescent light is imaged onto the light valve device.

2. A phosphor converter receiving excitation light emitted by a source of polarized excitation light, the phosphor converter comprising:

a phosphor material located on the surface of a reflector and a light pipe integrator system,

the phosphor material, when irradiated by the excitation light, emitting fluorescent light having a different spectrum than a spectrum of the excitation light;

a light pipe integrator system comprising a light pipe integrator;

the light pipe integrator having a first surface through which the excitation light enters the light pipe integrator and a second surface through which the excitation light exits the light pipe integrator;

the light pipe integrator system positioned relative to the source and the phosphor material such that;

when the source outputs excitation light, the first surface of the light pipe integrator receives the excitation light;

when excitation light exits the second surface of the light pipe integrator,

the excitation light is imaged onto the phosphor material;

the light pipe system positioned such that, when the phosphor material emits fluorescent light, the second surface of the light pipe integrator is positioned to receives a majority of the fluorescent light and the fluorescent light is transmitted to the first surface of the light pipe integrator.

3. The phosphor converter of claim 2, wherein a mild diffuser is positioned such that the excitation light is diffused by the diffuser prior to being received by the phosphor converter.

4. The phosphor converter of claim 2, wherein the light pipe integrator system comprises a tapered light pipe integrator.

5. The phosphor converter of claim 4, the light pipe integrator system further comprising an exit lens, wherein the exit lens is positioned adjacent the first surface of the tapered light pipe integrator, and the exit lens is configured to transform light bundles exiting the first surface of the tapered light pipe integrator to be telecentric.

6. The phosphor converter of claim 2, wherein:

the light pipe integrator system further comprises a lens system;

the lens system positioned between the light pipe integrator and the phosphor material; and

the lens system comprises lenses, the lenses configured to create an image of the illuminated part of the phosphor material onto the second surface of the light pipe integrator.

7. The phosphor converter of claim 6, the lens system further comprising a spherical reflector, wherein the spherical reflector is positioned relative to the phosphor material such that, when the phosphor material emits fluorescent light, the spherical reflector captures a part of the fluorescent light emitted by the phosphor material in a direction that is not captured by the lenses of the lens system and/or a part of the excitation light that is diffusively reflected by the phosphor material, and reflects that light back to the phosphor material, the phosphor material configured to scatter fluorescent light reflected by the spherical reflector such that the light is added to the emitted fluorescent light in random directions and/or to absorb part of the excitation light reflected back by the spherical reflector and emit additional fluorescent light in random directions.

8. The phosphor converter of claim 2, further comprising:

a reflective polarizer positioned in the light path between the polarized excitation light source and the phosphor material, wherein the reflective polarizer transmits light exhibiting a same polarization as the excitation light and reflects light exhibiting an orthogonal polarization as the excitation light, the fluorescent light exhibiting a mix of the same polarization as the excitation light and the orthogonal polarization as the excitation light;

the phosphor material configured to scatter fluorescent light reflected by the reflective polarizer such that the polarization exhibited by the scattered fluorescent light exhibits both the same polarization as the excitation light and the orthogonal polarization as the excitation light.

9. The phosphor converter of claim 8, wherein the reflective polarizer is located in close proximity to the phosphor material.

10. The phosphor converter of claim 8, wherein the second surface of the light pipe integrator is positioned in close proximity to the phosphor material and the reflective polarizer is positioned in close proximity to first surface of the light pipe integrator.

11. The phosphor converter of claim 2, further comprising a heat sink, wherein the phosphor material is thermally coupled to the heat sink.

12. The phosphor converter of claim 10, wherein the heat sink comprises a liquid heat exchanger.

13. The phosphor converter of claim 2, wherein the source comprises a laser diode or an array of laser diodes.

14. The phosphor converter of claim 2, wherein:

the first surface of the light pipe integrator comprises a transmissive portion and a reflective portion for a defined range of wavelengths, including the wavelengths of the incident excitation light;

a dichroic coating covers the reflective portion of the first surface, the dichroic coating configured to reflect light having a spectrum in the spectrum of the excitation light and pass light having a spectrum in the spectrum of the fluorescent light emitted by the phosphor material; and

the transmissive portion of the first surface configured to allow the excitation light to enter the light pipe integrator.

15. The phosphor converter of claim 2, wherein a spectrum shifting dichroic element is positioned in the light path between the polarized excitation light source and the phosphor material, the spectrum shifting dichroic element configured to reflect the fluorescent light having a wavelength range in a lower part of the spectrum of the fluorescent light such that the reflected fluorescent light is directed onto the phosphor material, wherein the phosphor material absorbs the reflected fluorescent light and emits fluorescent light having longer wavelengths than the reflected fluorescent light.

16. The phosphor converter of claim 2, wherein the spectrum of the excitation light is between 400 nm and 495 nm and the spectrum of the fluorescent light is between 495 nm and 700 nm.

17. The phosphor converter of claim 2, wherein the phosphor material is a layer having a thickness of approximately 50 micrometers.

18. The phosphor converter of claim 2, wherein the length of the light pipe integrator is at least 50 mm.

19. The phosphor converter of claim 2, wherein a dichroic polarizing beam splitter is positioned such that, when the source emits excitation light, the excitation light is reflected by the dichroic polarizing beam splitter such that the excitation light enters the first surface of the light pipe integrator system, wherein the dichroic polarizing beam splitter is configured to reflect light having a spectrum of the excitation light and exhibiting one polarity, transmit light having the spectrum of the excitation light and exhibiting an orthogonal polarity, and transmit light having a spectrum in the spectrum of the fluorescent light emitted by the phosphor material.

20. The phosphor converter of claim 2, further comprising a quarter wave retarder to rotate the polarization direction of the excitation light when the excitation light is reflected at the position of the phosphor material.

21. The phosphor converter of claim 2, wherein a dichroic polarizing beam splitter is positioned such that, when the source emits excitation light, the excitation light is transmitted by the dichroic polarizing beam splitter such that the excitation light enters the first surface of the light pipe integrator system, wherein the dichroic polarizing beam splitter is configured to transmit light having a spectrum of the excitation light and exhibiting one polarity, reflect light having the spectrum of the excitation light and exhibiting an orthogonal polarity, and reflect light having a spectrum in the spectrum of the fluorescent light emitted by the phosphor material.

22. A laser-phosphor light source, the light source comprising:

a source of polarized excitation light;

a phosphor converter receiving the excitation light;

the phosphor converter comprising;

a phosphor material located on the surface of a reflector;

the phosphor material, when irradiated by the excitation light, emitting fluorescent light having a different spectrum than a spectrum of the excitation light;

a reflective polarizer positioned in the light path between the polarized excitation light source and the phosphor material, wherein the reflective polarizer transmits light exhibiting a same polarization as the excitation light and reflects light exhibiting an orthogonal polarization as the excitation light, the fluorescent light exhibiting a mix of the same polarization as the excitation light and the orthogonal polarization as the excitation light; and

the phosphor material configured to scatter fluorescent light reflected by the reflective polarizer such that the polarization exhibited by the scattered fluorescent light exhibits both the same polarization as the excitation light and the orthogonal polarization as the excitation light.

23. The laser-phosphor light source of claim 22, wherein a spectrum shifting dichroic element positioned in the light path between the excitation light source and the phosphor material, the spectrum shifting dichroic element configured to reflect the fluorescent light having a wavelength range in a lower part of the spectrum of the fluorescent light such that the reflected fluorescent light is directed onto the phosphor material, wherein the phosphor material absorbs the reflected fluorescent light and emits fluorescent light having longer wavelengths than the reflected fluorescent light.

24. A spectrum-shifted phosphor light source comprising:

a source of excitation light;

a phosphor converter receiving the excitation light;

the phosphor converter comprising;

a phosphor material located on the surface of a reflector,

the phosphor material, when irradiated by the excitation light, emitting fluorescent light having a different spectrum than a spectrum of the excitation light;

a spectrum shifting dichroic element positioned in the light path between the excitation light source and the phosphor material, the spectrum shifting dichroic element configured to reflect the fluorescent light having a wavelength range in a lower part of the spectrum of the fluorescent light such that the reflected fluorescent light is directed onto the phosphor material, wherein the phosphor material absorbs the reflected fluorescent light and emits fluorescent light having longer wavelengths than the reflected fluorescent light.

25. A method for phosphor conversion of received polarized excitation light using a phosphor material and a light pipe integrator system, wherein the light pipe integrator system comprises a light pipe integrator, the method comprising:

directing the excitation light into the light pipe integrator system, wherein;

the excitation light enters a first surface of the light pipe integrator;

the excitation light propagates from the first surface of the light pipe integrator to a second surface of the light pipe integrator;

the excitation light exits the second surface of the light pipe integrator; and

the light pipe integrator system images the excitation light onto the phosphor material;

irradiating the phosphor material with the excitation light exiting the light pipe integrator system such that the phosphor material emits fluorescent light having a different spectrum than a spectrum of the excitation light;

directing the fluorescent light emitted by the phosphor material to enter the light pipe integrator system, wherein the fluorescent light enters the second surface of the light pipe integrator; and

directing the fluorescent light to pass through the light pipe integrator and exit the light pipe integrator via the first surface.

26. A method for outputting polarized fluorescent light using phosphor conversion of received polarized excitation light using a phosphor material and a reflective polarizer, the phosphor material is located on a surface of a reflector, and the reflective polarizer transmits light exhibiting a same polarization as the excitation light and reflects light exhibiting an orthogonal polarization as the excitation light, the method comprising:

directing the excitation light to pass through the reflective polarizer prior to irradiating the phosphor material;

irradiating the phosphor material with the excitation light passing through the reflective polarizer such that the irradiated phosphor material emits fluorescent light having a different spectrum than a spectrum of the excitation light, the fluorescent light emitted by the phosphor material exhibiting both the same polarization as the excitation light and the orthogonal polarization as the excitation light;

passing the fluorescent light exhibiting the same polarization as the excitation light through the reflective polarizer;

reflecting towards the phosphor material, by the reflective polarizer, the fluorescent light exhibiting the orthogonal polarization as the excitation light;

altering, due to scattering caused by the phosphor material, the polarization exhibited by the fluorescent light reflected by the reflective polarizer, such that;

the fluorescent light scattered by the phosphor material exhibits both the same polarization as the excitation light and the orthogonal polarization as the excitation light; and

after multiple cycles of reflection by the polarizer and scattering by the phosphor material, the majority of the fluorescent light will exit the reflective polarizer with the same polarization as the excitation light.

27. A method for outputting spectrum shifted fluorescent light using phosphor conversion of received excitation light using a phosphor material and a spectrum shifting dichroic element, the method comprising:

directing the excitation light to pass through the spectrum shifting dichroic element prior to irradiating the phosphor material;

irradiating the phosphor material with the excitation light passing through the spectrum shifting dichroic element such that the irradiated phosphor material emits fluorescent light having a different spectrum than a spectrum of the excitation light;

the spectrum shifting dichroic element passing the fluorescent light having a wavelength range in an upper part of the spectrum of the fluorescent light;

the spectrum shifting dichroic element reflecting the fluorescent light having a wavelength range in a lower part of the spectrum of the fluorescent light such that the reflected fluorescent light is directed onto the phosphor material, wherein the phosphor material absorbs the reflected fluorescent light and emits fluorescent light having longer wavelengths than the reflected fluorescent light.