SHARED-PATH ILLUMINATION AND EXCITATION OPTICS APPARATUS AND SYSTEMS

• US 20160191869A1
• Filed: 12/28/2014
• Published: 06/30/2016
• Est. Priority Date: 12/28/2014
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Bhakta, Vikrant R.
• Granted Patent: US 9,554,101 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 26/008 in the form of devices for effecting sequential colour changes, e.g. colour wheels
• CPC Class Codes: G02B 27/0927 Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
• CPC Class Codes: G02B 27/0994 Fibers, light pipes optical fibers per se G02B6/02
• CPC Class Codes: G02B 27/4244 in wavelength selecting devices spectrometry G01J
• CPC Class Codes: G02B 6/0005 the light guides being of the fibre type G02B6/0003 takes precedence
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type
• CPC Class Codes: G03B 21/208 Homogenising, shaping of the illumination light
• CPC Class Codes: H04N 9/3111 for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• CPC Class Codes: H04N 9/3158 for controlling the spectrum

Abstract

A Gaussian-distributed excitation light beam of an excitation spectrum emitted from an excitation light source enters a light pipe and is there converted to a top-hat spatially distributed excitation beam. The top-hat distributed excitation beam is focused on a phosphor-coated or reflective portion of a surface of an optical wavelength conversion element. Fluoresced and reflected beams travel outward from the wavelength conversion element and re-enter the light pipe to be homogenized during transit through the light pipe. A homogenized fluoresced or reflected beam is relayed to an output as one of a sequence of colors of homogenized light. The functions of Gaussian to top-hat conversion of the excitation beams directed toward the optical conversion element and homogenization of beams directed outward from the optical conversion element are both efficiently performed using a single, shared light pipe.

Claims

1. An illumination apparatus, comprising:

at least one electromagnetic excitation energy source to emit an excitation beam of a substantially Gaussian spatial distribution (“

Gaussian excitation beam”

) to include wavelengths in an excitation spectrum;

an optical wavelength conversion element optically coupled to the electromagnetic excitation energy source, a portion of an emitting surface of the wavelength conversion element coated with at least one of a fluorescent phosphor or a reflective surface, the fluorescent phosphor to receive a top-hat spatially distributed excitation beam and to generate at least one fluoresced beam of photons of at least one fluoresced spectrum, the reflective surface to reflect the top-hat spatially distributed excitation beam, the fluoresced beam or the reflected beam to be generated with a predetermined periodicity during at least one predetermined period of time; and

a light pipe optically coupled to the excitation energy source to receive the Gaussian excitation beam, to re-distribute power across an area of the Gaussian excitation beam corresponding to a width of the Gaussian excitation beam in order to form a substantially top-hat spatially distributed excitation beam, the light pipe optically coupled to the wavelength conversion element to homogenize the fluoresced beam or the reflected Gaussian excitation beam.

2. The illumination apparatus of claim 1, further including:

a condensing and collimation optical element group optically coupled to the optical wavelength conversion element to direct the top-hat spatially distributed excitation beam to the wavelength conversion element and to direct the fluoresced beam or the reflected Gaussian excitation beam back to the light pipe.

3. The illumination apparatus of claim 1, the light pipe formed in a tapered shape, the shape narrowing toward the optical wavelength conversion element to direct the top-hat spatially distributed excitation beam to the optical wavelength conversion element and to direct the fluoresced beam back into the light pipe.

4. The illumination apparatus of claim 1, the optical wavelength conversion element being a wheel capable of spinning, the emitting surface being a flat surface of the wheel, at least a portion of at least one of a plurality of radial sectors of the wheel surface coated with the fluorescent phosphor to emit the fluoresced beam of photons, the predetermined periodicity determined by an angular velocity of the phosphor-coated portion and the predetermined period of time determined by the arc length of the phosphor coated portion while illuminated by the top-hat distributed excitation beam.

5. The illumination apparatus of claim 4, at least one portion of at least one radial sector being a reflective surface to reflect the top-hat distributed excitation beam back to the light pipe.

6. The illumination apparatus of claim 5, the reflective portion of the radial sector fabricated with a set of microstructures selected from a group consisting of a Fresnel grating and a set of radial grooves, the set of microstructures to disperse the reflected top-hat spatially distributed excitation beam across a greater angle outward from the surface of the wheel than would be the angle of dispersion without the microstructures.

7. The illumination apparatus of claim 1, the excitation spectrum including wavelengths associated with ultraviolet (“

UV”

) light.

8. The illumination apparatus of claim 7, further including:

a dichroic mirror optically coupled to the light pipe to pass a beam of light of the UV excitation spectrum to the light pipe and to reflect the homogenized fluoresced beam received from the light pipe to an output.

9. The illumination apparatus of claim 1, the excitation energy source being an array of excitation energy sources positioned around a longitudinal axis of the light pipe, the longitudinal axis perpendicular to the emitting surface of the optical wavelength conversion element.

10. The illumination apparatus of claim 9, the excitation spectrum corresponding to a color selected from a group consisting of blue and ultraviolet (“

UV”

) light.

11. The illumination apparatus of claim 9, further including:

a switchable Bragg grating to pass light corresponding to the excitation spectrum during first predetermined time periods and to block light corresponding to the excitation spectrum during second predetermined time periods in order to prevent unconverted excitation energy from passing into an output beam during the second predetermined time periods.

12. The illumination apparatus of claim 9, further comprising:

at least one reflector optically coupled to the light pipe to direct the excitation beam from the excitation energy source to the light pipe.

13. The illumination apparatus of claim 12, the reflector being a transmissive plate with a reflective coating along a periphery of the plate.

14. The illumination apparatus of claim 13, a transmissive portion of the transmissive plate being a switchable Bragg grating to pass light corresponding to the excitation spectrum during first predetermined time periods and to block light corresponding to the excitation spectrum during second predetermined time periods in order to prevent unconverted excitation energy from passing into an output beam during the second predetermined time periods.

15. The illumination apparatus of claim 9, further including:

an image relay optics group optically coupled to the light pipe to direct the homogenized fluoresced beam to an output.

16. The illumination apparatus of claim 1, further including:

a first optical condenser optically coupled to an excitation input end of the light pipe to direct the excitation beam to the excitation input end of the light pipe; and

a second optical condenser optically coupled to a fluoresced beam input end of the light pipe to direct the fluoresced beam to the fluoresced beam input end of the light pipe.

17. An illumination apparatus, comprising:

at least one electromagnetic excitation energy source to emit an excitation beam of a substantially Gaussian spatial distribution (“

Gaussian excitation beam”

) to include wavelengths in an excitation spectrum;

an optical wavelength conversion element optically coupled to the electromagnetic excitation energy source, at least one portion of an emitting surface of the wavelength conversion element coated with a fluorescent phosphor to receive a substantially top-hat distributed excitation beam and to generate at least one of a fluoresced beam of photons of a fluoresced spectrum or a reflected top-hat spatially distributed excitation beam with a predetermined periodicity during at least one predetermined period of time; and

a tapered light pipe, a wide end of the tapered light pipe optically coupled to the excitation energy source to receive the Gaussian excitation beam and to re-distribute power across an area of the Gaussian excitation beam corresponding to a width of the Gaussian excitation beam in order to form the substantially top-hat distributed excitation beam and a narrow end of the tapered light source optically coupled to the wavelength conversion element to homogenize the fluoresced beam or the reflected Gaussian excitation beam to form at least one of a homogenized fluoresced beam or a homogenized reflected Gaussian excitation beam.

18. An image generation system, comprising:

at least one electromagnetic excitation energy source to emit an excitation beam of a substantially Gaussian distribution (“

Gaussian excitation beam”

) to include wavelengths in an excitation spectrum;

an optical wavelength conversion element optically coupled to the electromagnetic excitation energy source, a portion of an emitting surface of the wavelength conversion element coated with at least one of a fluorescent phosphor or a reflective surface, the fluorescent phosphor to receive a top-hat spatially distributed excitation beam and to generate at least one fluoresced beam of photons of at least one fluoresced spectrum, the reflective surface to reflect the top-hat spatially distributed excitation beam, the fluoresced beam or the reflected beam to be generated with a predetermined periodicity during at least one predetermined period of time;

a light pipe optically coupled to the excitation energy source to receive the Gaussian excitation beam, to re-distribute power across an area of the Gaussian excitation beam corresponding to a width of the Gaussian excitation beam in order to form a substantially top-hat spatially distributed excitation beam, the light pipe optically coupled to the wavelength conversion element to homogenize the fluoresced beam or the reflected Gaussian excitation beam;

a condensing and collimation optical element group optically coupled to the optical wavelength conversion element to direct the top-hat spatially distributed excitation beam to the wavelength conversion element and to direct the fluoresced beam or the reflected Gaussian excitation beam back to the light pipe;

a digital micro-mirror device (“

DMD”

) optically coupled to the light pipe, the DMD to include a two-dimensional set of micro mirrors to receive the homogenized fluoresced beam and to create a pixel image primary color frame by directing a portion of the homogenized fluoresced beam corresponding to each mirror into an image output path to generate a bright pixel of a color corresponding to the fluoresced spectrum or away from the image output path to generate a dark pixel; and

a synchronization and sequencing circuit communicatively coupled to the wavelength conversion element and to the DMD to synchronize the periodicity and on time of each fluoresced beam of a given wavelength with a state of the DMD during the on time and to sequence multiple fluoresced beams of wavelengths corresponding to each primary color to the DMD to generate a time-multiplexed full color pixel image.

19. The image generation system of claim 18, further comprising:

a first optical condenser optically coupled to an excitation input end of the light pipe to direct the excitation beam to the excitation input end of the light pipe; and

a second optical condenser optically coupled to a fluoresced beam input end of the light pipe to direct the fluoresced beam or the reflected top-hat spatially distributed excitation beam to the fluoresced beam input end of the light pipe.

20. The image generation system of claim 18, further comprising:

at least one image relay optical element group optically coupled to the light pipe and to the DMD to transfer the homogenized fluoresced beam to the DMD.