1. Field of Invention
The present invention relates to a device and method for testing light emitted by and transmitted through a luminescent film.
2. Description of Related Art
Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
A light emitting device is often combined with one or more wavelength converting materials such as phosphors to create white light. All or only a portion of the light emitted by the LED may be converted by the wavelength converting materials. Unconverted light emitted by the LED may be part of the final spectrum of light, though it need not be. Examples of common combinations include a blue-emitting LED combined with a yellow-emitting phosphor, a blue-emitting LED combined with green- and red-emitting phosphors, a UV-emitting LED combined with blue- and yellow-emitting phosphors, and a UV-emitting LED combined with blue-, green-, and red-emitting phosphors. Other wavelength converting materials may be added to tailor the spectrum.
It is an object of the invention to provide a device and method for testing a luminescent film.
In embodiments of the invention, a structure for testing a luminescent film includes a Lambertian light source, an integrating sphere having an input port, and a measuring device. The Lambertian light source includes a mixing chamber having an input port and an output port, and a light emitter coupled to the input port. During testing the luminescent film is positioned between the output port of the mixing chamber and the input port of the integrating sphere. The measuring device is optically coupled to the integrating sphere.
A method according to embodiments of the invention includes positioning a Lambertian light source proximate a first surface of a luminescent film, positioning an opening in an integrating sphere proximate a second surface of the luminescent film, illuminating a portion of the film with the Lambertian light source, and measuring a property of light from the luminescent film collected by the integrating sphere. In some embodiments, after measuring a property of light from the luminescent film, a property of a portion of the luminescent film is altered in response.
In embodiments of the invention, a structure for testing a luminescent film includes a light source, a light collection device, and a measuring device. During testing the luminescent film is positioned between the light source and the light collection device. The measuring device is optically coupled to the light collection device.
In accordance with embodiments of the invention, devices and method for testing the properties of light from luminescent films are provided. One example of a luminescent film is formed as follows: one or more conventional powder phosphors are mixed with a binder such as acrylic or silicone to achieve a target phosphor density. The phosphor/binder sheet is formed to have a target thickness, for example by spinning the mixture on a flat surface or molding the phosphor sheet. Phosphor may be mixed with a binder in liquid form which is then cured or dried to form a flexible luminescent film. Another example of a luminescent film is a powder phosphor or other wavelength converting material that is sintered into a ceramic. Such a film may be sintered with the desired thickness or may be sawn from a thicker ceramic phosphor. The luminescent film may be flexible, as in the case of a phosphor/binder film, stretchable, or rigid, as in the case of a ceramic phosphor. Other wavelength converting materials besides phosphors may be used, such as for example dyes, quantum dots, or optically-pumped semiconductor materials such as III-V or II-VI materials. In the alternative the luminescent film may include light scattering elements e.g. TiOx or TiO2 particles. In yet another alternative the film may not be an optical film and may include only light scattering elements e.g. TiOx or TiO2 particles, without any wavelength converting materials i.e. without any phosphors, dyes, quantum dots, or optically-pumped semiconductor materials such as III-V or II-VI materials.
After testing, the luminescent film may be attached or laminated directly to a suitable light source, or it may be spaced apart from the light source, for example as part of a display. Examples of suitable light sources include but are not limited to blue- or UV-emitting III-nitride LEDs and laser diodes. Any other suitable light source may be used with the luminescent films tested by the devices and methods described herein.
A device for measuring the light is positioned on the other side of luminescent film 2. The measured light includes light emitted by the light source 14 and scattered by luminescent film 2 at the same wavelength, and light absorbed by luminescent film 2 and reemitted over a different wavelength range.
Luminescent film 2 is positioned between a port 13 of mixing chamber 12 and a port 17 of an integrating sphere 16. An integrating sphere is a hollow cavity with the interior coated with a highly diffuse reflecting material to cause uniform scattering. Integrating spheres are known in the art. One or both of port 13 and 17 may be knife-edge ports in some embodiments. In some embodiments, port 17 is larger than port 13, though they may be the same size or port 17 may be smaller than port 13. In some embodiments, the separation between ports 17 and 13 is no more than 1 mm. In some embodiments, the separation between portions 17 and 13 is such that luminescent film 2 is in sliding engagement with one or both ports. The surfaces of ports 17 and/or 13 in sliding engagement with luminescent film 2 may be electrically conductive.
Light captured by integrating sphere 16 may be coupled to a suitable measuring device 11 by, for example, a suitable light transmitting structure 10 such as a fiber bundle. Alternatively, measuring device 11 may be directly coupled to integrating sphere 16. Measuring device 11 may be, for example, a spectrometer or a photo colorimeter. Measuring device 11 may measure properties of the captured light such as, for example, the color, peak wavelength, full width at half maximum of the spectrum, total radiant flux, and/or luminous flux. Measuring device 11 may also measure the ratio of scattered, unconverted photons to converted photons. In some embodiments, the light source or a reference source may emit long-wavelength light that is not wavelength-converted by luminescent film 2 (for example, light at a peak wavelength greater than 650 nm in some embodiments) and measuring device 11 measures light through luminescent film 2, in order to characterize scattering by luminescent film 2.
The device illustrated in
In some embodiments, integrating sphere 16 is positioned on a mechanism that allows for removal and replacement without affecting alignment. For example, integrating sphere 16 may be mounted on a hinge which allows integrating sphere 16 to be lifted at the beginning of a production run. One end of a roll of a luminescent film 2 is placed over port 13, then integrating sphere 16 is brought back into its original position with luminescent film 2 disposed between port 17 and port 13. In some embodiments, integrating sphere 16 is positioned on kinematic or magnetic mounts for ease of removal and reproducible replacement. In some embodiments, one or both of integrating sphere 16 and mixing chamber 12 are mounted on springs which push ports 13 and 17 together in order to maintain sliding contact of both ports with luminescent film 2. An advantage to the use of springs is that ports 13 and 17 can be disposed in sliding contact with luminescent film 2 regardless of the thickness of luminescent film 2.
The devices illustrated in
In the device illustrated in
In the device illustrated in
The axis of illumination of luminescent film 2 by light emitter 3 is normal or substantially normal to the plane of luminescent film 2 in some embodiments. The illuminated beam is nearly collimated with a numerical aperture (N.A.) below 0.2 in some embodiments. Similarly, the axis of collection optics 7 is normal or substantially normal to the plane of luminescent film 2 in some embodiments. In some embodiments, the acceptance cone created by collection optics 7 is narrow such that the collection N.A. is less than 0.2 in some embodiments and between 0.05 and 0.15 in some embodiments.
In some embodiments, imaging optics 4 and light emitter 3, and collection optics 7, aperture 8, and measurement head 9 are attached to a frame 1. Frame 1 is attached to a translation stage so frame 1 can be moved to sample different parts of a stationary luminescent film 2. In some embodiments, frame 1 is stationary and luminescent film 2 is moved, for example by rollers as illustrated in
The device illustrated in
In embodiments where the luminescent film 2 is stationary during measurement, the probed area of luminescent film 2 is equal to the spot size. In the devices of
In some embodiments, an additional optional tester 26 according to embodiments of the invention, which may be one of the devices illustrated in
Having described the invention in detail, those skilled in the art will appreciate that, given the present disclosure, modifications may be made to the invention without departing from the spirit of the inventive concept described herein. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described.
This application claims the benefit or priority of and describes relationships between the following applications: wherein this application is a continuation in part of U.S. patent application Ser. No. 13/885,774, filed May 16, 2013, which is the National Stage of International Application No. PCT/IB2011/055788, filed Dec. 19, 2011, which claims the priority of U.S. provisional application 61/425,805 filed Dec. 22, 2010, all of which are incorporated herein in whole by reference.
Number | Name | Date | Kind |
---|---|---|---|
5044754 | Cicchiello et al. | Sep 1991 | A |
5079678 | Parker | Jan 1992 | A |
5406070 | Edgar et al. | Apr 1995 | A |
5764352 | Kappel et al. | Jun 1998 | A |
5929994 | Lee et al. | Jul 1999 | A |
6222623 | Wetherell | Apr 2001 | B1 |
6963335 | Tanaka et al. | Nov 2005 | B2 |
8339025 | Nakamura et al. | Dec 2012 | B2 |
20040156981 | Ohno et al. | Aug 2004 | A1 |
20100301739 | Nakamura et al. | Dec 2010 | A1 |
20110041726 | Robb et al. | Feb 2011 | A1 |
Number | Date | Country |
---|---|---|
2757196 | Jun 1979 | DE |
1688704 | Aug 2006 | EP |
2429865 | Mar 2007 | GB |
1998-073486 | Mar 1998 | JP |
2000-186960 | Jul 2000 | JP |
2004-361149 | Dec 2004 | JP |
2009-128131 | Jun 2009 | JP |
WO-02071023 | Sep 2002 | WO |
Entry |
---|
CN OA2MO, Application 201180061920.9, LUM reference, Mar. 11, 2016, 25 pps. |
Number | Date | Country | |
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20150233827 A1 | Aug 2015 | US |
Number | Date | Country | |
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61425805 | Dec 2010 | US |
Number | Date | Country | |
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Parent | 13885774 | US | |
Child | 14704007 | US |