111111
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`1111111111111111111111111111111111111111111111111111111111111
`US007390116B2
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`c12) United States Patent
`Jain
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,390,116 B2
`Jun.24,2008
`
`(54) HIGH-BRIGHTNESS, COMPACT
`ILLUMINATOR WITH INTEGRATED
`OPTICAL ELEMENTS
`
`(75)
`
`Inventor: Kanti Jain, Hawthorne, NY (US)
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,782,550 A * 7/1998 Ohashi eta!. ............... 362/507
`6,280,480 B1 * 8/2001 Tuttle et al .................. 362/518
`
`(73) Assignee: Anvik Corporation, Hawthorne, NY
`(US)
`
`* cited by examiner
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 148 days.
`
`(21) Appl. No.: 10/830,607
`
`(22) Filed:
`
`Apr. 23, 2004
`
`(65)
`
`(51)
`
`Prior Publication Data
`
`US 2005/0237764 Al
`
`Oct. 27, 2005
`
`Int. Cl.
`G02B 6100
`F21V 7100
`
`(2006.01)
`(2006.01)
`
`(52) U.S. Cl. ........................................ 362/551; 362/347
`
`(58) Field of Classification Search ................. 362/551,
`362/555,341,347,245
`See application file for complete search history.
`
`Primary Examiner-John A Ward
`(74) Attorney, Agent, or Firm-Carl C. Kling
`
`(57)
`
`ABSTRACT
`
`A compact, high-brightness, integrated illuminator in which
`collection oflight from a point-arc source is maximized by a
`multi-curvature reflector section configuration of elliptical
`reflector and segmented spherical retroreflector directing all
`light rays into a well-defined numerical aperture. The inven(cid:173)
`tion also integrates a homogenizer and other optical elements
`with the multi-curvature reflector section, constructs any or
`all of these components in a single block of optical material,
`or, alternatively, constructs these components with molded
`hollow reflective cavities fabricated in metal or plastic blocks.
`Cooling is provided by internal fluid channels within the
`block.
`
`8 Claims, 11 Drawing Sheets
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`1
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`2
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`U.S. Patent
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`Jun.24,2008
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`Sheet 1 of 11
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`US 7,390,116 B2
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`Fig. 1
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`1
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`2
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`U.S. Patent
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`Jun.24,2008
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`Sheet 2 of 11
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`US 7,390,116 B2
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`22
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`I 26
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`21
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`20
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`23
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`23
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`U.S. Patent
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`Jun.24,2008
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`Sheet 3 of 11
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`US 7,390,116 B2
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`20
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`20
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`23
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`46
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`51
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`45
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`47
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`49
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`43
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`Fig. 4
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`Fig. 5
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`U.S. Patent
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`Jun.24,2008
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`Sheet 4 of 11
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`US 7,390,116 B2
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`56
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`58
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`55
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`56
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`25
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`Fig. 6
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`45
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`Fig. 8
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`58
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`59
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`55
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`56
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`Fig. 7
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`Fig. 9
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`U.S. Patent
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`Jun.24,2008
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`Sheet 5 of 11
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`US 7,390,116 B2
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`55
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`45
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`58
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`59
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`55
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`56
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`Fig. 11
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`Fig. 12
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`U.S. Patent
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`Jun.24,2008
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`Sheet 6 of 11
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`US 7,390,116 B2
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`Fig. 13
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`74
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`70
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`75
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`71
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`Fig. 14
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`U.S. Patent
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`Jun.24,2008
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`Sheet 7 of 11
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`US 7,390,116 B2
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`74
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`70
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`75
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`66
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`70
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`74
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`75
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`71
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`71
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`66
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`Fig. 15
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`72
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`Fig. 16
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`U.S. Patent
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`Jun.24,2008
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`Sheet 8 of 11
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`US 7,390,116 B2
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`Fig. 17
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`Fig. 18
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`U.S. Patent
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`Jun.24,2008
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`Sheet 9 of 11
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`US 7,390,116 B2
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`Fig. 19
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`71
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`Fig. 20
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`U.S. Patent
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`Jun.24,2008
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`Sheet 10 of 11
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`US 7,390,116 B2
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`•
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`U.S. Patent
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`Jun.24,2008
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`Sheet 11 of 11
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`US 7,390,116 B2
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`Fig. 22
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`

`
`1
`HIGH-BRIGHTNESS, COMPACT
`ILLUMINATOR WITH INTEGRATED
`OPTICAL ELEMENTS
`
`FIELD OF THE INVENTION
`
`This invention relates to light sources and illumination
`systems for optical projection, and specifically relates to such
`applications in which it is important to maximize the light
`collection from a source lamp, to minimize the size and power
`requirement of the lamp, to make the spatial uniformity of the
`lamp's light beam high, and to collect the light within a
`specified numerical aperture so as to optimize the imaging
`performance of the projection system.
`
`BACKGROUND OF THE INVENTION
`
`US 7,390,116 B2
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`2
`situated at a focus point of the elliptical reflective surface,
`which causes the reflected rays to be directed toward the other
`focus point of the ellipse, enabling them to enter a beam(cid:173)
`uniformization device at a desired numerical aperture. In all
`such light sources, the requirement of maximum collection
`efficiency on the one hand and a well-defined numerical aper(cid:173)
`ture on the other hand cannot both be met optimally. This is so
`because, to maximize light collection, one must use as large a
`portion of the elliptical surface as possible, whereas to con-
`10 fine the reflected rays to the desired numerical aperture, one
`must limit the extended arc of the reflector.
`
`SUMMARY OF THE INVENTION
`
`A key subsystem in optical systems for a variety of appli(cid:173)
`cations is an illumination system which comprises a light
`source, such as an arc lamp, and several optical components,
`such as mirrors and lenses, to collect, shape and relay the light
`from the source to the desired destination. For example, in a
`projector, light from an arc lamp is collected, made uniform,
`and made to illuminate an object, such as film or a program(cid:173)
`mable spatial light modulator, which is then imaged onto a
`display screen. As another example, in a lithography system,
`light from the light source is collected, made uniform, shaped
`into a specific cross-section, and is made to illuminate a
`photomask having a pattern. The mask is then imaged by a
`projection lens to a substrate, such as a semiconductor wafer 30
`or a display panel, coated with a layer of photosensitive
`medium.
`In all these applications, the intensity of the light illumi(cid:173)
`nating the object must be very uniform spatially. The object,
`as stated earlier, is, for example, a spatial light modulator 35
`(SLM) chip in a projector, or a photomask in a lithography
`system. Spatial uniformity of a light beam means that the
`cross-sectional profile of the intensity must be substantially
`flat. A second important requirement on the illumination sys(cid:173)
`tem is that its efficiency must be as high as possible so that 40
`loss of light is minimized and the smallest possible light
`source may be used. Alternatively, the highest possible
`energy may be obtained at the destination surface, such as the
`display screen or the semiconductor wafer.
`Other highly desirable features in an illumination system 45
`include compact size and self-luminosity. The importance of
`a compact size of the illumination system is self-evident-it
`enables the whole optical system to be compact, and there(cid:173)
`fore, low-weight, more portable, etc. Self-luminosity of a
`light source means it is equivalent to an emission surface on 50
`which every point behaves effectively as an emission point
`from which light rays emanate in a specific numerical aper(cid:173)
`ture. Such a characteristic is especially important when the
`illuminated object must be subsequently imaged with high
`resolution onto another surface. All of the above desirable 55
`features of illumination systems are important in the case of
`digital projections, lithography systems, and numerous other
`optical systems.
`A self-luminous emission surface is readily obtained by
`transformation of a high-brightness, point-like light source
`by use of suitable optical elements. A widely used, high(cid:173)
`brightness, point-like light source is a high-pressure, com(cid:173)
`pact, Hg (or Hg-Xe) arc lamp. To increase the amount of
`collected radiation, and direct it toward the object, such an arc
`lamp is usually manufactured with a built-in elliptical reflec(cid:173)
`tor. An elliptical reflector has two focus points, which I shall
`call "near focus" and "far focus." The point-arc of the lamp is
`
`15
`
`This invention eliminates the need for a trade-off, in an
`illumination system, between the two desired requirements(cid:173)
`collection efficiency and well-defined NA. This invention
`provides a light source configuration with the maximum pos-
`20 sible light collection efficiency, and directs all the collected
`light into the pre-designed numerical aperture. Further, the
`disclosed configuration also provides integration of an uni(cid:173)
`formizer device into a single compact module. Finally, the
`reflector housing and body are so designed that cooling chan-
`25 nels can be built into the lamp construction for cooling the
`lamp, with air or with a liquid in a closed-loop system.
`This invention discloses a construction for a compact arc
`lamp in which collection of light from a point-arc source is
`maximized by a multi-curvature reflector section configura(cid:173)
`tion in such a way that not only all of the collected radiation
`is focused at a point, but it is also directed into a well-defined
`numerical aperture. The invention also shows how such a
`high-efficiency lamp is integrated with an intensity homog(cid:173)
`enizer, making it possible to provide a compact, integrated
`light source for applications in projectors, displays, projec(cid:173)
`tion television, and exposure systems. As illustrated in FIG. 1,
`a point-arc source 1 is placed at the near focus 2 of an elliptical
`reflector 3, which directs the reflected rays (e.g., 4) to the far
`focus 5 of the ellipse 6. The arc-extent (from 7 to 8) of the
`elliptical reflector 3 is such that the outermost light rays
`(reflected from near its perimeter, e.g., 9) define the desired
`numerical aperture a, for the radiation. I shall therefore call
`them "intra-NA rays." All other light rays, which I shall call
`"extra-NA rays," in prior art lamp designs would be lost
`because they would not be directed to the far focus 5 of the
`ellipse. The loss of such rays could be reduced by extending
`the arc of the elliptical reflector, but then the numerical aper(cid:173)
`ture of the collected rays would increase beyond the desired
`angle. In this invention, the loss of these "extra-NA rays" is
`eliminated by constructing the lamp reflector as follows:
`The NA-defining arc of the reflector surface is made ellip(cid:173)
`tical, as stated. Beyond the solid angle subtended by this arc,
`the reflecting surface is extended by a series of spherical
`segments 10-13 whose center is the near focus 2 of the ellip(cid:173)
`tical surface. All extra-NA light rays striking these spherical
`segments (e.g., 14) are directed back toward and through the
`near focus 2, so that when they are then reflected by the
`elliptical surface behind the near focus, they are brought to a
`focus at the same far focus 5 of the ellipse where all the
`60 "intra-NA" rays, which were reflected directly by the ellipti(cid:173)
`cal surface, are focused. I shall call such a reflector an "Ellip(cid:173)
`SpheRetro Reflector," or ESR Reflector. The lamp construc(cid:173)
`tion of this invention thus nearly doubles the "useful" light
`efficiency of the lamp. In addition, as also illustrated in FIG.
`65 1, a solid light-tuunel homogenizer 15 is integrated with the
`reflector enclosure, rendering the integrated unit extremely
`compact and manufacturable at a low cost. In the Detailed
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`US 7,390,116 B2
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`4
`FIG. 13 is a preferred embodiment of the invention show(cid:173)
`ing a short-arc lamp in a block enclosure that has an elliptical
`reflector surface, spherical retro-reflector segments, and a
`light-tunnel homogenizer section.
`FIG. 14 is an embodiment of the invention showing a
`short-arc lamp in a reflector block housing that also has an
`imaging lens.
`FIG. 15 is an illustration of a preferred embodiment of the
`invention, showing a short-arc lamp housed within a two-
`10 piece block assembly, the blocks fabricated to provide an
`elliptical reflector surface, a set of spherical retro-reflecting
`segments, a light tunnel homogenizer section, and an imaging
`lens.
`FIG. 16 illustrates the construction details of the embodi(cid:173)
`ment ofFIG. 15, showing how the entire assembly is made of
`two molded sections.
`FIGS. 17 and 18 present three-dimensional perspectives of
`the illustrations of FIGS. 15 and 16.
`FIG. 19 is an illustration of a preferred embodiment of the
`invention, showing a short-arc lamp housed within a two(cid:173)
`piece block assembly, the blocks fabricated to provide an
`elliptical reflector surface, a set of spherical retro-reflecting
`segments, a fly' s-eye-lens homogenizer combined with a col(cid:173)
`limating lens, and an imaging lens.
`FIG. 20 illustrates the construction details of the embodi(cid:173)
`ment ofFIG. 17, showing how the entire assembly is made of
`two molded sections.
`FIG. 21 is an illustration of a preferred embodiment of the
`invention, showing a short-arc lamp housed within a two(cid:173)
`piece block assembly, the blocks fabricated to provide an
`elliptical reflector surface, a spherical retro-reflecting seg-
`ments, an energy-recycling light tunnel homogenizer section,
`and an imaging lens.
`FIG. 22 is a preferred embodiment of the invention show-
`35 ing a short-arc lamp in a block enclosure that has an elliptical
`reflector surface, spherical retro-reflector segments, and an
`energy-recycling solid light-tunnel homogenizer section.
`
`30
`
`25
`
`3
`Description of the Embodiments, I describe several such
`reflector designs and integration configurations.
`An object of the invention is to make useful all of the light
`from an arc lamp by combining an elliptical reflector with a
`set of concentric spherical retro-reflector segments.
`A feature of the invention is the positioning of the center of
`the spherical reflector segments, at the near focus of the
`elliptical reflector, to retain the numerical aperture.
`Another feature of the invention is the segmenting of the
`spherical reflector to maintain the focus at the near focus of
`the elliptical reflector while minimizing the outer envelope of
`the segmented spherical reflector and thus the overall size of
`the lamp-reflector subassembly.
`Still another feature is the combination of homogenizer
`with elliptical reflector and spherical retro-reflector segments 15
`for compact configuration.
`Yet another feature is the embodiment of the combination
`of homogenizer with elliptical reflector and spherical retro(cid:173)
`reflector segments as a solid block of material for good ther(cid:173)
`mal management characteristics and easy manufacturability. 20
`An advantage of the invention is the high brightness of the
`lamp with high efficiency of light collection.
`Another advantage of the invention is its integrated con(cid:173)
`figuration that combines a lamp and reflectors with uni-
`formizer and other optical elements.
`Yet another advantage of the invention is its compactness
`consistent with good optical and heat-dissipation qualities.
`Other objects, features and advantages will become clear to
`those skilled in the art during reading of the following text and
`perusal of the attached drawings.
`
`FIGURES
`
`FIG. 1 is a schematic illustration of the concept of the
`invention, showing a short-arc lamp in a reflector cavity with
`an elliptical forward-reflecting surface, spherical retro-re(cid:173)
`flecting segments, and with a joined intensity homogenizer.
`FIG. 2 shows a prior-art arc-lamp with an elliptical reflec(cid:173)
`tor, illustrating how a majority of the forward-emitted rays
`from the lamp are not collected.
`FIG. 3 is a further illustration of a prior-art lamp, showing
`how an extension of the elliptical reflector does not improve
`collection of forward-emitted rays.
`FIG. 4 is a schematic of one of the embodiments of the
`invention, showing a short-arc lamp with an elliptical reflec(cid:173)
`tor and a spherical retro-reflector for collection of all the
`forward-emitted rays.
`FIG. 5 is an illustration of a preferred embodiment of the
`invention, showing a short -arc lamp in a reflector housing, the
`reflector having an elliptical section and several spherical
`retro-reflecting segments.
`FIG. 6 is an illustration of another preferred embodiment of
`the invention, showing a short-arc lamp within a reflector
`block enclosure made of two blocks, the reflector surface
`having an elliptical section and spherical segments.
`FIGS. 7 and 8 are illustrations of the end views of the
`embodiment of FIG. 6.
`FIGS. 9 and 10 are illustrations of the end views of an
`embodiment of the invention similar to that of FIG. 6, except
`that the outer perimeter of the cross-section of the reflector
`block assembly is circular rather than square.
`FIG. 11 illustrates an embodiment of the invention show(cid:173)
`ing a short-arc lamp in a reflector block assembly similar to
`that of FIG. 6 but with the addition of built-in cooling chan(cid:173)
`nels.
`FIG. 12 is an end-view of the embodiment of FIG. 11.
`
`40
`
`DETAILED DESCRIPTION OF THE
`EMBODIMENTS
`
`45
`
`Arc lamps are used as light sources in a wide variety of
`applications, such as electronic data projectors, film projec(cid:173)
`tors, projection televisions, and exposure systems for micro(cid:173)
`electronics fabrication. A typical prior-art construction of an
`arc lamp is shown in FIG. 2. It comprises a short-arc, high-
`pressure, Hg or Hg-Xe discharge lamp 20, with an elliptical
`reflector 21, and is sealed with a window 22 in the front. The
`point-arc of the lamp is placed at the near-focus 23 of the
`50 reflector's elliptical surface. Light rays incident on the reflec(cid:173)
`tor surface are directed toward the far focus 24 of the ellipse,
`from where they may be directed toward an object surface in
`various prior-art ways, such as with a positive lens 25. Note
`that among all the rays emitted by the lamp, the effectively
`55 useful rays are only those that first reach the point 24 and are
`then directed by lens 25, i.e., only the rays emitted by the arc
`that first strike the elliptical reflector. Therefore, all the rays,
`such as 26-31, emitted in a forward cone defined by the angle
`~'are not collected, and are thus lost. Note that these lost rays
`60 cannot be collected by simply extending the elliptical arc(cid:173)
`extent of the reflector-as shown in FIG. 3. If the elliptical
`reflector arc is extended by the portion 3 2 so as to prevent ray
`30 from escaping, then ray 30 will be intercepted, and, after
`reflection as ray 33, will reach the far focus 24. Even so, rays
`65 such as ray 33 still will not be collected by lens 25 because
`they are extra-NA light rays, outside the collectible NA, and
`therefore will be lost. Depending upon the lamp dimensions,
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`US 7,390,116 B2
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`5
`these lost rays may constitute a third or half of the total
`radiation emitted by the lamp. Thus, if these otherwise lost
`rays could be effectively collected, the useful light efficiency
`of the lamp could be increased by as much as a factor of 2.
`Such is the improvement made possible by the invention
`described in this application.
`Effective Collection of"Extra-NA" Light Rays
`At the outset, let me clarify the distinction between "effec(cid:173)
`tive collection" and mere collection oflight rays. Referring to
`FIG. 3, the light ray 30, upon reflection from the elliptical 10
`reflector segment 32, is collected as ray 33 and directed to the
`focus point 24, but such collection is not useful because ray 33
`is not accepted by lens 25. When a ray emitted by the lamp arc
`is so directed that it is within the acceptance cone of the lens
`25, i.e., it is an intra-NA ray, within the specified numerical 15
`aperture, I shall term its collection as "effective collection."
`Now I describe how the extra-NA rays can be effectively
`collected, thereby increasing the effective brightness and effi(cid:173)
`ciency of the lamp substantially.
`FIG. 4 illustrates the basic principle of the new Ellip- 20
`SpheRetro (ESR) lamp concept. The lamp envelope is
`designed to include not only the elliptical reflector 21, which
`collects, as before, all the intra-NA rays, but also a spherical
`reflector 35 whose arc-extent is such that it captures all the
`extra-NA rays such as rays 36-43. Further, the curvature and 25
`placement of the spherical reflector 35 are such that its center
`is the same as the near focus 23 of the elliptical reflect 21.
`Therefore, an extra-NA ray, such as ray 37, is retro-reflected
`by the spherical reflector 21, travels through the near focus
`23, is reflected by the elliptical reflector 21, is directed as ray 30
`44 through the same far focus 24, and is angularly confined
`within the specified NA. Thus, by capturing nearly all the
`extra-NA rays which otherwise would be lost, this ESR
`reflector lamp nearly doubles the radiation delivered to the
`imaging lens 25 within the desired numerical aperture. Note 35
`that the window 22 which previously (see FIG. 3) functioned
`as the front face of the lamp enclosure, is now not necessary;
`it is therefore eliminated and, instead, a window 45 is pro(cid:173)
`vided as a seal on an opening in the spherical reflector 35. I
`will describe other embodiments of the lamp construction 40
`shortly.
`Compact ESR Reflector Lamp Configuration
`Note that in the embodiment of the invention illustrated in
`FIG. 4, the incorporation of the spherical retro-reflector
`nearly doubles the size of the overall enclosure of the lamp,
`which is not a desirable consequence. Such an increase in the
`lamp size is prevented by the embodiment shown in FIG. 5.
`Here, the previous spherical reflector 35 is broken up into
`several spherical segments 46-51. Each of the spherical seg(cid:173)
`ments 46-51 has a curvature and position such that its center
`is at the same near focus 23 of elliptical reflector 21. Addi(cid:173)
`tionally, the partitioning of the previous spherical reflector 35
`into the new spherical segments 46-51 is done in such a way
`that it becomes possible to place the new segments as close as
`possible to the outermost rays 52 and 53. These outermost
`rays 52 and 53 define the specified numerical aperture a. Note
`that, constructionally, each pair of equivalent spherical seg(cid:173)
`ments, e.g., 46 and 51, are together a strip-slice of a spherical
`shell. Additionally, note that the largest-radius segments 48
`and 49 are constructionally a spherical disc, and that this disc
`has a hole in the center where the far focus of the elliptical
`reflector 21 is situated; this hole is sealed with the optical
`window 45, as shown in FIG. 5.
`Block Configuration with Reflector Cavity
`The ESR Reflector lamp design illustrated in FIG. 5 may be 65
`readily constructed in practice as a block enclosure in which
`the reflector surface is realized by forming a cavity. This is
`
`6
`illustrated in FIGS. 6, 7 and 8. The full enclosure is made as
`two halves 55 and 56, each of which has one-half of the lamp
`cavity hollowed out from inside and coated with a durable,
`high-reflectivity coating. The elliptical reflector surface is
`indicated by 60 and the spherical reflector segments by 61-63.
`FIG. 7 is an end-view of the lamp, looking at FIG. 6 from
`the left, and FIG. 8 is the end-view of the lamp looking from
`the right. The perimeter of the cross-section of the enclosure
`is shown as a square (FIGS. 7 and S).As an alternate embodi(cid:173)
`ment, the perimeter can be circular, as illustrated in FIGS. 9
`and 10. The two half-blocks of the enclosure can be joined
`with each other using a suitable high-temperature adhesive
`along the interface 57. Provision is made on the left end-faces
`(FIGS. 7 and 9) for an end of the arc lamp discharge tube 58
`and electrodes 59 to emerge. On the right end-faces, the
`transparent window 45 is suitably sealed.
`High-Brightness-Lamp Enclosure with Cooling
`Since the high-brightness lamp configurations shown in
`FIGS. 6-10 dissipate 100-200 W of power, it is highly desir(cid:173)
`able to provide a built-in cooling mechanism in their enclo(cid:173)
`sures. The constructions illustrated in FIGS. 6-10 enable very
`convenient incorporation of cooling channels, as shown in
`FIGS. 11 and 12. The cooling charmels may be formed at the
`time the half-blocks are molded, and run through the solid
`walls of the reflector half-blocks. The cooling fluid may be
`air, water, ethylene glycol solution or some other suitable
`coolant. The channels may continue from one half-block to
`the other half-block, in which case appropriate fluid-tight seal
`is provided between the two half-blocks. Note that the path of
`the cooling channels, as well as their construction shown in
`FIGS. 11 and 12, is only one of may possible paths of embed(cid:173)
`ding the charmels in the reflector housing; various alternate
`but equivalent configurations can readily be devised by one
`even cursorily knowledgeable in the art.
`In some optical devices, when rays emitted from a point
`source are directed back to the source, some instability of the
`source or excessive heating may occur. In an arc lamp of the
`type envisioned here, the typical size of the emission region is
`1-2 mm, for which such undesirable effects are not expected
`to occur. However, to eliminate such a possibility entirely, the
`spherical retro-reflector segments can be readily designed to
`be slightly off their perfect position or curvature so that the
`retro-reflected rays are focused suitably offset from, but close
`to, the near-focus of the elliptical reflector.
`ESR Lamp with Homogenizer
`The compact high-brightness lamp with the ESR reflector
`described above can be further enhanced in functionality by
`integration of an intensity homogenizing component, as illus-
`50 trated in FIG. 13. The reflector unit is configured as before,
`i.e., as a combination of an elliptical reflector 60 and seg(cid:173)
`mented spherical retro-reflectors 61-64, integrated as a block
`assembly 65, as in FIG. 6. But now, in addition, the block
`assembly 65 also includes a cylindrical cavity 66, whose
`55 internal surface is mirrorized, and which acts as an intensity
`uniformizer. The cylindrical cavity 66 functions as a light
`tunnel with internally reflective walls. All the light rays emit(cid:173)
`ted from the arc lamp and collected by the elliptical and
`spherical reflectors are focused near the entrance to the light
`60 tunnel homogenizer 66. These light rays enter light tunnel
`homogenizer 66 as shown in FIG. 13. The light rays get
`randomly mixed, by multiple reflections within the homog(cid:173)
`enizer, so that the spatial intensity distribution at the exit plane
`68 of the homogenizer is highly uniform.
`Note that the homogenizer turmel is sealed by a transparent
`window 45 at the exit plane. The exit plane 68 of the homog(cid:173)
`enizer may now be conveniently imaged by a lens 25 onto the
`
`45
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`Energetiq Ex. 2077, page 15 - IPR2015-01377
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`US 7,390,116 B2
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`7
`desired object surface. Suitable cooling channels may be
`provided in the reflector block assembly as described previ(cid:173)
`ously, with FIGS. 11-12.
`ESR Reflector Lamp with Integrated Lens
`In the embodiment of FIG. 6, I have shown a lamp enclo(cid:173)
`sure made of two reflector blocks 55 and 56 and a transparent
`window 45. In addition, an external lens 25 is used to direct
`the collected rays to the object surface. I now illustrate how
`the entire assembly can be further simplified and made easier
`to fabricate at a lower cost by integrating the lens as a part of 10
`the reflector blocks and eliminating the window, as shown in
`FIG. 14. The lamp enclosure is made of two reflector blocks
`70 and 71, and the lens 72 is made a part of one of them (70).
`Note that the lens 72, as a part of block 70, is brought into
`contact with block 71 at interface 73; keeping the body of the 15
`lens free of additional interfaces enables it to have high opti-
`cal performance.
`Note that only the elliptical (74) and spherical (e.g., 75)
`retro-reflector portions of the internal surface of each block
`are mirrorized. In addition, the surfaces of the lens 72 may be 20
`coated with an anti-reflection coating to minimize unwanted
`reflectionlosses.Also, as in the embodiments ofFIGS.ll and
`12, cooling channels may be fabricated in the blocks 70 and
`71.
`Elliptical-Spherical Lamp with Integrated Homogenizer
`and Lens
`The embodiments described in FIGS. 13 and 14 may be
`combined to provide a new embodiment in which the lamp
`enclosure is integrated with both a homogenizer and a lens;
`this is illustrated in FIGS. 15-18. The entire assembly is 30
`constructed of two blocks 70 and 71. Each block has one-half
`of the elliptical reflector 74, the spherical retro-reflector seg(cid:173)
`ments (e.g., 75) and the homogenizer tunnel 66. The lens 72
`is made entirely a part of block 70, as shown in FIG. 16, and
`makes contact with block 71 at interface 73. Again, cooling
`channels may be provided in the body of each block. The
`surfaces of the reflectors and homogenizer are mirrorized.
`The lens surfaces are anti-reflection coated.
`In all of the embodiments above in which a light-tunnel
`homogenizer is incorporated (e.g., FIGS. 13 and 15) it is also
`possible to provide a different type oflight homogenizer as an
`alternative to the light-turmel type 66. For example, in FIGS.
`19 and20, I illustrate how a fly's-eye lens type ofuniformizer
`76 may be fabricated as a part of one of the two blocks 70 and
`71 that make up the lamp enclosure assembly. As before, I
`show the elliptical reflector as 74, one of the spherical retro(cid:173)
`reflector segments as 75 and the imaging lens as 72. The
`fly's-eye lens array 76 is a two-dimensional array of small
`lenslets and is readily fabricated by well-established molding
`processes. The lens array 76 comes in contact with block 71 at
`interface 77. Note that I have also shown the input surface
`(left side) 78 of the fly's-eye lens array 76 as a convex surface;
`this serves to collimate the rays inside the body of the fly's(cid:173)
`eye lens array. Many other alternate configurations are pos(cid:173)
`sible, such as fabricating a collimating lens separately or
`using two fly's-eye lens arrays.
`Compact, High-Efficiency Lamp with Integrated Energy(cid:173)
`Recycling Homogenizer
`The efficiency and brightness of the compact ESR illumi(cid:173)
`nator shown in FIG. 15 can be further enhanced by providing
`an energy-recycling feature in the homogenizer 66. This is
`especially important in the use of such an illuminator in, for
`example, an electronic data projector or a projection televi(cid:173)
`sion where the lamp power, compactness and brightness are
`significant criteria in product design. In a color projector, the
`white light from the illuminator first passes through a color
`filter unit, which is usually a color wheel with red, green and
`
`8
`blue spiral bands. Each band transmits only one color. For
`example, light of only red frequency passes through the red
`band, the rest (approximately two-thirds of the total) being
`reflected and lost. By using a recycling homogenizer, the
`reflected rays are captured and re-utilized, as illustrated in
`FIG. 21.
`In FIG. 21 a ray 80 leaves the elliptical reflector 74, enters
`the homogenizer 66, is reflected from the bottom homog(cid:173)
`enizer wall 83, emerges from imaging lens 72 as ray 81, and
`strikes color filter unit 79. The frequencies oflight that do not
`pass through filter 79 are reflected as ray 82, which, traveling
`in the reverse direction, passes through the imaging lens 72,
`re-enters the homogenizer 66, is reflected from the bottom
`homogenizerwall83 as ray 84, and strikes the inner side 85 of
`the homogenizer input face. The inner face 85 is mirrorized,
`so the ray 84 is reflected as ray 86, which is now traveling in
`the forward direction, and emerges from imaging lens 72 as
`ray 87, thus being re-utilized. The energy-recycling feature of
`this embodiment can increase the efficiency and brightness of
`the illuminator by a factor of two or more. To maximize the
`energy recycling multiplier, the area of the homogenizer inner
`face 85 must be made as large as possible, and therefore, the
`entrance hole 88 as small as possible. Note that the minimum
`size of entrance hole 88 will be determined by the focus spot
`25 size of the elliptical reflector 74, and therefore also on the size
`of the point arc 2 of the lamp 1. I remark that t