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Researchers Submit Patent Application, "Phosphor Wheel Illumination Using Laser Light Reflective Region", for Approval

September 4, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventor Khan, Sajjad Ali (Plano, TX), filed on January 16, 2014, was made available online on August 21, 2014.

No assignee for this patent application has been made.

News editors obtained the following quote from the background information supplied by the inventors: "This relates to generation of sequential color illumination in solid state laser projection systems and the like.

"An example solid state projector using blue lasers and a phosphor color wheel as an illumination source and a spatial light modulator for modulation of the emitted light is described in Patent Application Pub. No. US 2013/0242534 A1, published Sep. 19, 2013, entitled 'Projector Light Source and System, Including Configuration for Display of 3D Images,' the entirety of which is incorporated herein by reference. Such system utilizes blue lasers as a direct source of blue color light and utilizes the blue lasers as an indirect source of other color light by energizing other color light producing phosphors with the blue color light from the blue lasers. Efficient blue lasers available for use in such solid state projectors are, however, often not of suitable wavelength to create a pleasing blue color when observed displayed on a screen or other display surface.

"A typical phosphor color wheel as used in the described solid state projector has arcuate segments coated with different color emitting phosphors annularly positioned at circumferentially angularly spaced locations about a circular wheel. An example color wheel having circular tracks or bands of different color emitting phosphors spaced at different concentric radially spaced locations is described in Patent Application Pub. No. US 2011/0211333 A1, published Sep. 1, 2011, entitled 'Wavelength Conversion,' the entirety of which is incorporated herein by reference.

"The use of cyan phosphor in combination with blue laser light to form a more pleasing blue in a sequential color illumination system that utilizes a blue light wraparound path is described in Application No. 61/752,294 filed Jan. 14, 2013, entitled 'Method of Utilizing a Cyan Phosphor to Color Correct a Laser Illuminated Projection System,' the entirety of which is incorporated herein by reference."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventor's summary information for this patent application: "A color sequential illumination system for image projection that uses blue laser light in a wraparound path and emitted light from blue laser light excited phosphor segments of a rotating color wheel for generation of other colors is described in application Ser. No. 13/652,129, incorporated herein. The described wraparound path, however, requires additional lenses and mirrors (five lenses and three mirrors for the arrangement illustrated in the '129 application) which adds to system volume and cost.

"The instant approach utilizes dichroic materials having polarization selective properties in the laser light reflecting (viz., blue color reflecting/longer wavelength transmitting) dichroic filter to improve the appearance of blue color without the need for a long wraparound path. In one implementation, 3 dB cutoff points for the dichroic filter are chosen based on the laser polarization and dichroic properties. In one approach, an enhanced blue color may be obtained utilizing a thin layer of blue/cyan/green phosphor material to modify the blue color point. This enables availability of a wider color gamut than with use of blue laser diode alone.

"The described implementation enables a blue color illumination at lower cost (eight optical components and mechanics) in a smaller size and volume than illumination systems using a longer wraparound path for blue laser light redirection. Use of a thin layer of phosphor material together with the blue laser for generation of the blue color enables a more visually pleasing blue and wider color gamut than obtained with blue laser light redirection alone. Speckle and scintillation may be reduced by using a diffuse reflective surface for the blue segment instead of a flat surface. A thin layer of green/cyan/blue phosphor should also help. It may be that the described implementation will also result in fewer blue pump watts needed as the blue segment size may be reduced to allow for more time for other colors, giving lower cost and higher lm/W efficiency.

"In the described implementation, a dichroic filter is used that is shifted left (e.g., shifted by 39 nm towards shorter wavelength) as compared to a same type filter used in a standard arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 illustrates an example illumination system embodying aspects of the principles disclosed herein.

"FIG. 2 illustrated reflectance and transmittance spectra for an example 45.degree. angle dichroic filter usable with the illumination system of FIG. 1."

For additional information on this patent application, see: Khan, Sajjad Ali. Phosphor Wheel Illumination Using Laser Light Reflective Region. Filed January 16, 2014 and posted August 21, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=3813&p=77&f=G&l=50&d=PG01&S1=20140814.PD.&OS=PD/20140814&RS=PD/20140814

Keywords for this news article include: Patents.

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Source: Politics & Government Week


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