Patent Application
20090021131
All research and development associated with this invention has been performed using private funds. No federally sponsored research or development has been used.
1. Field of Invention
The present invention relates to a design that improves the efficiency of an incandescent lamp and a design that converts an incandescent or gas discharge lamp to output a predominately linear polarized output by converting the radiation to a single linear polarization. The techniques can be used in synergy or independently. High efficiency lamps with linear polarized output are desirable in several applications such as in an LCD projector or potentially automobile headlights.
2. Description of Related Art
U.S. Pat. No. 4,539,505 Leslie A. Riseberg et. al., replaces the metal tungsten incandescent filament with resistive carbon doped candoluminescent material filament that heats to luminescence when an electrical current is applied. The candoluminescent filaments are lower temperature visible light generating sources. The lower temperature is possible because visible light is generated via luminescence rather then black body radiation. The product never became available on the market, which suggests it was not viable.
U.S. Pat. No. 5,124,286 John P. Edgar, et. al. describes the chemical content of a candoluminescent mantle for gas lamps. Visible light energy is generated by the heating action of the mantle by gas combustion. Edgar teaches the compositions of the different salts to be formed in the mantle to support candoluminescent action. Thorium is thus avoided which has the disadvantage of being radioactive.
U.S. Pat. No. 4,535,269 Charles D. Tschetter et. al. introduces use of a discriminative reflective filter formed to reflect and direct the wasted radiation to the filament for energy recycling. The design advantage is to provide a reflective discriminative filter, which allows the desirable wavelengths to transmit through the filter, and recycling of the wasted energy. The disadvantage is the difficulty of returning the energy to the filament, which is a small spatial target. The optical alignment accuracy required to recycle the energy to the filament makes the lamp not viable in the market place.
U.S. Pat. No. 5,160,199 Franaco Berti, describes a halogen lamp reflector wherein Franaco Berti teaches the basic geometric assembly of a projector light with a reflector and placement of the lamp and lamp filament. The reflector shape best supports a square output. A rectangular LCD pattern requires optics to fill the different projection pattern, which limits the projection to be mainly square.
U.S. Pat. No. 7,237,900 Ci Guang Peng et. al. describes a polarization conversion system using a technique that separates the polarizations, and redirects the wasted polarization to a phase retardation plate and recombines with the desired polarization. The technique requires quarter wave plates, which are wavelength specific, and complex optics geometry. The quarter wave plates need also be precisely placed in position and rotation. The major disadvantage is the complexity and precise micro positioning required to make the optic.
U.S. Pat. No. 7,312,913 Dec. 25, 2007 Serge Bierhuizen describes use of a reflective mirror polarizer and wavelength specific filters that reflect the wasted wavelengths and transmit the desirable wavelengths. For polarization recycling, the light is funneled through light tubes causing polarization randomization by multiple reflections off of the inner light tube surface prior to being redirected back to the exit apertures. The structure is complicated and accordingly expensive to fabricate. The light tubes are also funneled causing divergence and loss of directivity.
U.S. Pat. No. 6,208,451 Yoshitaka Itoh describes a polarization conversion system using a micro array that separates the polarizations and directs the unwanted polarization through a polarization conversion optic and recombines the energy with the desirable polarization. These techniques require a micro array of precise optics positioned and aligned. The quarter wave plates need also be precisely placed in position and rotation, and are difficult to fabricate, which increases costs.
U.S. Pat. No. 6,101,032 Wortman, et. al. describes use of a reflective polarizing mirror on the output of a fluorescent or incandescent lamp, used to reflect unwanted polarization back to within the lamp wherein the diffuse inner surface of the lamp causes polarization randomization on interactions, and subsequent exit at the desired polarization. The diffuse source consists of a light emitting region consistent with a fluorescent lamp with its inner coating which acts as a large scattering and depolarizing region. Wortman utilizes a diffuse surface, which is not consistent with a tungsten or gas discharge lamp. The drawings accordingly support a fluorescent lamp source rather than an incandescent tungsten or gas discharge lamp. Wortman describes a reflective filter returning wasted orthogonal polarization back to an incandescent light source; however, what is neglected is the very small spatial size the tungsten element projects, and accordingly the very small reabsorbtion of wasted orthogonal polarization. Wortman specifies lambertian reflection rather than specular reflection for the polarization randomization. Thus the reflected radiation that was nearly colliminated is also randomized in direction, which marginalizes its usefulness in applications such as an LCD projector or automobile headlight, which requires a directed output. For application to a incandescent lamp, polarization randomization is achieved if the filament source acts as a diffuse source and rejected polarization is returned to the filament for randomization. The filament is very small, which means the useful conversion is very small. Wortman neglects the capability of a dielectric coating on the reflector being able to randomize the polarization and maintain directivity of the returned orthogonal polarization, which has use for a tungsten or gas discharge lamp wherein the light source is spatially very small disallowing efficient reabsorbtion of the wasted energy by the filament or gas discharge arc.
U.S. Pat. No. 6,710,921 Hansen, et. al. describes a method to separate the polarizations using a reflective polarization mirror and redirect the wasted orthogonal polarization to a half wave plate for polarization conversion, then recombine the recycled polarization. The optic is a micro optic array and is difficult to build which drives cost.
U.S. Pat. No. 7,352,119 Berlin, describes an elliptical gas discharge lamp reflector for video projection. The shape is in the direction of the output illumination which provides a circular output pattern rather than a rectangular pattern.
U.S. Application Number. No. 61/128,298 of May 21, 2008 Stark, describes a method to convert polarization by use of reflection off of dielectric multilayers.
What is described is an incandescent filament lamp or gas discharge lamp, for example, xenon with improved efficiency that can also be designed to output a linear polarized illumination at a high efficiency; the linear polarized output being desirable for use in an LCD projector and other instruments requiring linear polarized illumination such as automobile headlights. The lamp is composed of a electromagnetic source such as a filament or gas discharge, a reflector to direct the radiation generated by a filament or gas discharge into a directed output aperture, discriminative filters placed at the aperture reflect unwanted polarization and wavelengths back toward the source, with the addition of a candoluminescent structure, which acts as a secondary electromagnetic radiation output source when heated by outputting desirable wavelengths while being at a lower operating temperature than a tungsten filament. The optical coating on the reflector acts to randomize the reflected polarization while maintaining the specular nature of the reflection thus preserving the collimination and redirecting the radiation back to the output aperture. One or more of these techniques can be added to the lamp's design. The polarization conversion technique can be added to any lamp type wherein a reflector and a polarization mirror can be arranged.
The candoluminescent recycling techniques can also be readily applied to a general service lamp wherein columniation is not required, or linear polarized output light is not required. The candoluminescent material when placed in proximity to the filament or other light generating heat source is heated by the source and converts the heat directly to desirable wavelengths, adding to the lamp's color rendering and efficiency.
The candoluminescent envelope, 10, may also be placed in other positions such as outside of the filament. Multiple configurations of 10 are reasonable in the same lamp, not shown.
The lamp, 20, is positioned inside the reflector, 31. The reflector, 31, acts to direct the output radiation, 100, generated by the lamp, 20, in a nearly colliminated manner to the output aperture. Positioned over the output aperture is a polarized mirror reflector, 40, which allows a single polarization to exit, 102, while reflecting the orthogonal polarization, 101, shown as the dotted line. The polarization filter, 40, may also be part of the lamp assembly or a second structure positioned at the lamps output aperture as shown. The orthogonal polarized ray, 101, is returned toward the lamp, 20 by the polarization filter, 40, which recycles 101 in several manners. The reflected ray's energy is recycled in a small degree by being absorbed by the filament, but it is preferable to miss the filament and internal lamp structure because of the low recycling efficiency gained. The reflected orthogonal ray, 101, is primarily recycled by reflection off of the reflector wherein the polarization is randomized by the dielectric multilayer coating, which is the most efficient recycling technique, and redirected back to the output aperture. The interaction with the reflector is specular in nature, which preserves the rays directivity, and redirects the ray 101 back to the output aperture wherein the cycle is repeated. The specular reflection is a major advantage over a diffuse reflection, which would also randomize the light path direction. Other coatings may be used on the reflector, which also randomizes the polarization such as metal with a coating; however these are not as efficient reflectors as a dielectric multilayer, which can be better than 99% reflectivity. A complex coating using a grated etched film may also be utilized, but the additional complexity does not offer sufficient benefit. Thus between the reflector 31 and polarization mirror 40, a polarized light trap is created that allows one polarization to escape through the output aperture and randomizes the trapped polarization for recycling when reflecting off of the dielectric multilayer on reflector 31. The reflections off of the reflectors dielectric multilayer coating convert the trapped orthogonal polarization to the desired polarization for output. The reflection efficiencies for the dielectric coating on the reflector 31, and on the polarization mirror can be very high, allowing for high polarization conversion efficiency. The multiple reflections between the polarization mirror, 40, and the reflector, 31, act to homogenize the light intensity spatially, providing a more even output illumination. If candoluminescent material is also present, any wasted polarization striking the candoluminescent material will act to heat the candoluminescent material and add to the lamp's efficiency; however, this effect is less efficient as the direct polarization conversion by reflection. The same is true for radiation impacting the tungsten filament, 22.
Briefly, a second energy recycling technique is use of a wavelength discrimination filter referred to as a dichroic reflector, 41, which reflects the wasted radiation such as infrared and transmits the desirable radiation such as visible. Items 10 and 41 provide the greatest efficient improvement for wasted wavelength energy recycling; however, can also contribute in a minor way to polarization recycling and may both be part of the lamp design, as shown. In detail, item 41 is a discriminative wavelength filter which allows the desirable wavelengths, such as visible, to transmit and reflects the wasted energy such as infrared. The dielectric coating on the inner part of 31 is designed to reflect the wasted wavelength energy and maintain directivity, which directs the energy, in the path shown as 101, back in a minor part to the filament, 22, and primarily to the candoluminescent container, 10. The reflected energy following a similar ray trace as 101 is partially absorbed by the filament, and primarily by the candoluminescent material inside of 10 wherein the energy is recycled via emission from the filament and emission via candoluminescence. A heat trap is formed by item 41 and 31 to convert the wasted energy into desirable wavelengths. The positions of 40 and 41 may be interchanged, and also may be part of the lamp design. Current projector lamp design used a dichroic filter with alternating layers of TiO2 and SiO2 that reflect greater than 99% if the visible light and transmit 90% of the infrared through the reflector which is made of a transparent material. The lamp is referred to as a cool lamp because the infrared is transmitted away from the projected visible radiation. If only polarization recycling is opted, the same cool lamp design is utilized using only the addition of the polarization mirror, 40 to the current design.
The candoluminescent material is placed in such a manner to maximize heating from all sources. The tungsten filament provides direct heating, therefore the candoluminescent material is placed in the center of the tungsten filament; however, this is not particularly necessary. The placement also takes advantage of the existing reflection paths between the lamp reflector, 31 and the dichroic filter, 41. Other placements are possible.
The polarization and wavelength conversion methods when both used constitute an example with greatest improved efficiency; however, either of one method may be utilized singularly.
The configuration shown is applicable to the tube style floor lamps and shows a method to recycle energy without the use of reflectors.
The candoluminescent envelope, 10, may also be placed in other arrangements such as outside of the filament. Multiple configurations of 10 are reasonable in the same lamp, not shown.
Output radiation 100, generated by 60, reflects off of 30 and is directed to the polarization mirror 40. The polarization mirror passes the desirable linear polarization, 102, and reflects the orthogonal polarization shown by ray trace 101. Ray trace 101 reflects via specular reflection off of the inner dielectric coating on 32 wherein the polarization is randomized by the dielectric coating while the directivity is maintained. Ray path 101 is redirected back to the output aperture and polarization mirror 40, wherein the cycle is repeated. The dielectric is best composed of birefringent layers so that the P polarization, which predominantly enters internally to the multilayers, has its polarization randomized by the birefringent crystals that are part of the dielectric multilayer, such as rutile form of TiO2. Both P and S polarizations to a degree are reflected by the internal action of the multilayer, and both polarizations are randomized.
The candoluminescent structure, 10 is chiefly useful to recycle wasted wavelengths. By being in near proximity of the tungsten filament it is heated to output desirable radiation via candoluminescence. The addition of a wavelength discriminative filter, 41, over the output aperture recycles wasted wavelength energy such as infrared by directing the energy into the candoluminescent material inside of 10. The electrical connection tab, 21, is shown similar to an existing projection lamp, but is not of critical form to the design.
The shape for an LCD projection application can be either elliptical or spherical, depending on the desired output projection shape.
Wavelength and candoluminescent material structures may also be added; however, the geometry requires the dichroic wavelength filter have some form to direct the wasted energy to a candoluminescent button. In this manner the two recycling techniques are more independent and do not augment each other.
The present application is a continuation-in-part (CIP) of patent application Pub. No. U.S. Ser. No. 08/919,641, filed Aug. 8, 1997, now U.S. Pat. No. 6,268,685, issued Jul. 31, 2001 all of which are incorporated herein in their entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 08919641 | Aug 1997 | US |
| Child | 12217474 | US |
