Faceted totally internally reflecting lens with curved faces

BACKGROUND OF THE INVENTION

0001This invention relates generally to radiant, particularly electromagnetic, energy concentration, redirection, and manipulation, and improves over the subject matters of U.S. Patent 4,377,759 and of an article "Compact non-imaging Lens with Totally Internally Reflecting Facets" by W. Parkyn et al. in SPIE, Vol. 1528, pages 70 to 81. It more particularly concerns a system for employing a transparent means with elements thereof using Total Internal Reflection (TIR), in conjunction with refraction; such elements acting in concert with purely refractive elements (as those in a Fresnel lens) and/or metal mirrors to redirect radiant energy to or from a predetermined zone or zones; such redirection having a predetermined degree of concentration and/or chromatic dispersion. The zones have sources of light, as in photoillumination, or radiant energy receiving means for conversion of the redirected energy to thermal, electric, chemical, or mechanical forms. Alternatively, a further transparent means is employed, with elements thereof having the same design principle (TIR) as above; said further transparent means acting as a secondary radiation redirector for the purpose of magnifying the degree of concentration and/or chromatic dispersion of the radiant energy redirected by the primary transparent means.

0002The prior art of radiant energy concentration and illumination in general consists of two major types, as exemplified by refractive and reflective astronomical telescopes: a refractive lens positioned in front of a receiver or light source, or a retro-reflective mirror positioned behind a receiver or light source. The corresponding devices in the prior art of solar energy concentration are the Fresnel lens and the parabolic reflector, which focus solar energy on a target. Furthermore, there are non-imaging, reflecting concentrators that have the advantage of fixed daily (non-tracking) position with only seasonal adjustments, but the disadvantage of requiring relatively large reflector areas and delivering only relatively low energy concentrations.

0003Fresnel lenses are devices comprising purely refractive elements, but they have physically inherent limitations of redirecting radiant energy that give high f/ratios and bulky concentrator structure. Moveover, linear Fresnel lenses have, for off-angles in the direction of the grooves, focusing errors, that are also inherent in the laws of refraction, and that limit one-axis tracking configurations to relatively low concentration.

0004Parabolic reflector concentrators have seen widespread use, but are subject to losses of received radiant energy because the receiver is situated between the source and the reflector, which is thereby shaded, preventing in particular the utilization of large heat engines at the focus. Furthermore, the receiver is exposed to environmental degradation and thermal losses, and the inclusion of a protective transparent cover means about the receiver will merely reduce the system's optical efficiency.

0005Another reflecting system has appeared in the literature, as repoded by Rabl in <u>Solar Energy</u>, Vol. 19, No. 5. It employs a retro-reflecting means with elements that have two TIR faces to redirect radiant energy out the same side as it came in. Its only improvement over a metal mirror of the same shape is a potentially higher reflectivity; but the double internal reflection doubles the sensitivity to manufacturing error over that of the present invention, which redirects radiant energy through itself with only a single reflection.

0006Moreover, US-A-4 299 201 discloses a solar energy focusing means which is formed as a semicylinder and which includes a plurality of rulings and areas to define a multiplicity of essentially parallel facets extending longitudinally with respect to the focusing means.

0007In addition, US-A-4 069 812 discloses a solar concentrator and energy collection system comprising a curved prismatic, Fresnel-type lens. As can in particular be gathered from Fig. 10 of this document, the single prisms have three curved faces in the cross-section parallel to the incident rays.

0008Document "IX. Internationaler Schifffahrts-Congress, Düsseldorf - 1902, Mitteilung von Walter Körte: 'Fortschritte auf dem Gebiet des Seezeichenwesens'" discloses in a figure designated as "Bl.III" a Fresnel type radiant energy redirecting system. In a radially outer portion, this known system comprises separate prismatic catadioptric elements which have an entry face, a totally internally reflecting face and an exit face. The central portion of this known system is formed by a contiguous body which comprises multiple radiant energy redirecting facets. These facets have a plane entry face and a curved exit face, but they do not have a totally internally reflecting face. Figures 3 to 5 of the article by Körte show embodiments of separate prismatic catadioptric elements having a totally internally reflecting face which defines a lens means and is concave toward the entry face, and an entry face which is convex toward the totally internally reflecting face.

0009Document DE 60 36 66 discloses a system comprising a radiant energy transmitting body means having a plurality of contiguous catadioptric elements. Each of the elements has a totally internally reflecting face, an entry face and an exit face which is formed by a part of an exit surface. The exit surface and the totally internally reflecting faces can be curved.

0010A radiant energy redirecting system comprising the features of the pre-characterizing clause of claim 1 is known from the article "Compact non-imaging Lens with Totally Internally Reflecting Facets" by W. Parkyn et al. in SPIE, Vol. 1528, pages 70 to 81.

0011It is a major object of the present invention to overcome the above-described problems of, and difficulties with, the prior art, and to provide a means to collect and employ radiant energy in a very cost-effective and efficient manner, using a new basic tool with applications that include the collection, concentration, redirection and wavelength separation.

0012According to the present invention, the above objects are achieved by the radiant energy redirecting system according to claim 1.

0013The present invention is basically characterized by the use of a transparent means employing elements to redirect radiant energy by means of TIR in conjunction with refraction, such means being positioned between the radiant energy source and a receiver. Each element redirects radiant energy upon a common target zone or zones, during the energy's internal passage through the element. A properly oriented ray enters through the entry face and strikes the reflective face, which redirects it toward the exit face. In addition, a lens means is associated with the entry and the TIR face.

0014Accordingly, the present invention is characterized by the passage of redirected radiant energy entirely through the transmitting body means and out the opposite side from which it entered after transmission via associated lens means. This invention constitutes a third class of radiant energy concentrators that also has applications to other forms of radiant energy redirection than concentration, such as wavelength separation or collimation. Other surfaces of the element may be inactive for the ray of interest (e.g., diffuse skylight of off-angle sunlight).

0015While TIR alone is limited to incident angles greater than the critical angle and therefore to any redirective bend angles less than 180°-2 critical angle (about 96° for acrylic), additional redirection is possible with or without wavelength separation by non-normal angling of the entry and exit faces. Such large bend angles enable a given diameter transparent means to be much closer to the target than a means limited to refraction alone, thereby greatly reducing the necessary support structure. Furthermore, a transparent means employing up to 90° bend angles can utilize a flat mirror extending from the target to the rim of the means, thereby doubling solar concentration or doubling intercept efficiency for a light source.

0016The first of the present invention's improvements over the subject matter of U.S. Patent 4,337,759 is the curvature of the faces of the individual lens elements. This curvature may be provided at the TIR face and the entry face or all three of the faces (entry, exit and TIR). Radiant energy handling is thus improved over a flat-faceted face system, as for example in redirection of rays from a line or point source, within constraints of interior shadowing and TIR face slope, to produce either parallel or converging output beams in a system using multiple faces. Also, improvements in ray collimation and focusing are realized; and design freedom is enhanced, since each face can be individually curved or various combination of face curvatures can be employed to minimize aberrations, due to the finite size of the facets. For ease of quality control of manufacturing, the curved facet faces can form spheres with centers on the axis of rotational symmetry of the lens. When the axially symmetric lens is made by molding a rigid material, undercut interior faces are precluded, which limits the curvature of those faces. This constraint is not applicable to elastomeric lens materials.

0017The facet design of the TIR lens has four degrees of freedom: the angle of the entry face, the angle of the TIR face, the angle of the exit face, and the position of the inwardly adjacent facet. A full design solution requires that four requirements be used to derive these four angles. In many of the designs illustrated below, prearranged choices restricted the degrees of freedom. In general, however, the requirements are: <ul id="ul0001" list-style="none" compact="compact"><li>a) the redirection of light from sources to target;</li><li>b) the full interception of light by the TIR face;</li><li>c) the full illumination of the exit face, for maximum thermodynamic efficiency; and</li><li>d) the non-interference of a facet's input and output rays by the next facet inward.</li></ul>

0018Typically, a TIR lens is generated from the outermost, or rim, facet inward in a facet-by-facet, numerically controlled iteration. The four requirements form a set of nonlinear equations in four unknowns to be solved for their roots. Because there is no general method of solving such equations, typical computer routines apply matrix inversion method that assumes quasi-linearity in the neighborhood of the solution hyperspace. This requires some prior knowledge of this hyperspace so that a starting point for the solution search is within the quasi-linear regime. This prior knowledge depends upon whether the facet is triangular or quadrilateral. The former give wider interfacet slot angles and thus are easier to make; but the latter add another degree of freedom, enabling a wider choice of overall lens shapes. The angle of this fourth, optically inactive, side of the facet would typically be set at the minimum draft angle for pulling the lens from a mold (about 2°). In the case of small lenses with only a few facets, there is also the possibility of an adjacent facet being larger or smaller than its neighbors, in order to raise the lens height and improve collimation.

0019The relative facet positions, as determined by the non-interference criterion, determine the overall lens profile, which should be low or high depending upon the application. In a converging or collimating TIR illumination system, it is advantageous to have somewhat more lens height, so that the apparent size of the source is reduced at the central facets, and the output beam is thereby tightened. This consideration does not hold for diverging TIR lenses, because only efficiency, and not beam tightness, is required.

0020An important use of facet curvature is in a small TIR lens with only a few facets, such as a collimator for a light-emitting diode. Molding very small facets may be undesirable because of difficulties in making the mold. Curved facet faces enable relatively large facets to perform as accurately as small ones. Lenses for light-emitting diodes are of interest for red lamps at the rear of automobiles. In fact, the TIR lens can be incorporated into the conventional transparent cover of an LED, greatly improving its luminous efficiency.

0021The exit face can have about the same refractive bending as the entry face, preventing unwanted image magnification that broadens the focal spot. The individual convex curvature on each of the facet faces is vital to the success of this design: <ul id="ul0002" list-style="dash" compact="compact"><li>entry-face curvature enables the entire TIR face to be utilized, through a slight convergence that prevents any light from missing the TIR face;</li><li>TIR-face curvature enables the entire exit face to be illuminated, by preventing any light from striking stairstep risers or the adjacent TIR face; and</li><li>exit-face curvature focuses light onto the target, eliminating the effects of finite facet size.</li></ul>

0022This focusing configuration would have two prominent applications that considerably improve the light utilization efficiency of the prior art: <ul id="ul0003" list-style="bullet" compact="compact"><li>Imaging projectors for slides, motion pictures, or mi-crofiche. Current designs use ellipsoidal reflectors that have inherently low intercept efficiency (i.e., the fraction of the source output that actually ends up in the output image of the device). The TIR lens of the present invention can be used in conjunction with an aspheric lens in order to remove the cosine-4th illumination non-uniformity typical of the prior art. This version of the TIR lens typically has stepped exit faces, with the risers angled parallel to the converging rays, to ensure spatial continuity of the focal cone. The faces of the facets can be curved so as to augment the action of the auxiliary lens. </li><li>Another advantage of the TIR lens for this application is that it azimuthally smears out any structure in the source, removing a source of pattern noise that is inherent in the imaging action of an ellipsoidal reflector.</li><li>Illumination injector or optical fiber bundles and light pipes. Prior art here also uses ellipsoidal reflectors. The TIR lens would have a focal cone half angle matched to the acceptance angle of the target.</li><li>Light-gathering means for spectrometers that analyze the diffusely emitted light of samples that have been stimulated to produce Raman or fluorescent light. Conventional spectrometers typically collect this light with microscope objectives, which also deliver tightly focused (50 micrometers) laser light to the sample. These objectives typically have a focal length equal to their diameter, so that they subtend about 50° and collect 5% of the diffusely emitted output. The converging TIR lens can collect over half of this emission, a factor of ten improvement, greatly aiding spectral analysis because of the greater signal to noise ratio.</li></ul><ul id="ul0004" list-style="dash" compact="compact"><li>A TIR lens that redirects light from a source in order to form a diverging cone of light, as in floodlighting applications. For cone angles of 45° or less, this lens is more efficient than a conventional congruent reflector and much more compact. This divergence can either be for uniform illumination, or it can take the appearance of effectively coming from a virtual source located behind the lens, with appropriate facet-face curvatures compensating for the different distances of the facets from the source.</li><li>A collimating TIR lens made of silicon. Because of the high refractive index of this material, the refractive faces of its facets would be somewhat differently angled than those of a glass lens. The application for a silicon lens is for the collimation of infrared light and the exclusion of visible light (because silicon absorbs all wavelengths shorter than 1.1 micrometers). The purpose of this application is the jamming of the guidance sensors of heat-seeking, anti-air-craft rockets by focused beams of pulsating infrared light. The prior art uses much less efficient parabolic reflectors in conjunction with a silicon window. The silicon TIR lens would be an important new kind of infrared illuminator, as found in many night-vision systems.</li></ul>

0023The superiority of the present invention can be seen in its application to redirection of rays from a point source, concentration of spherical or plane waves, better collimation than parabolic mirrors, and more efficient focusing than ellipsoidal mirrors.

0024These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which:

DRAWING DESCRIPTION

0025<ul id="ul0005" list-style="none" compact="compact"><li>Fig. 1 is a vertical section in elevation showing one form of a conventional apparatus;</li><li>Fig. 2 is a vertical section in elevation showing another form of a conventional apparatus;</li><li>Fig. 3 is an enlarged section on lines 3-3 or Fig. 2;</li><li>Figs. 4<u>a</u>--4<u>e</u> are enlarged sections through elements of various configurations;</li><li>Fig. 5 is a view like Fig. 1 showing a portion of a solar optical concentrator of-somewhat different and employed configuration;</li><li>Fig. 6 is a schematic showing two devices, operating in conjunction, one of which is like that of Fig. 1 or 5, and the other being a collimator;</li><li>Fig. 7 is an enlarged section through a collimator as used in Fig. 6;</li><li>Figs. 8-11, 13, 14 and 15 are schematics showing different applications of the radiant energy concentrating means;</li><li>Figs. 12<u>a</u> and 12<u>b</u> are fragmentary sections showing modified concentrators; Figs 16a to 16c are sections producing light rays of varying angularity, as shown;</li><li>Fig. 17 is a section showing a further modified radiant energy concentrating means for use with a light emitting diode;</li><li>Fig. 18 is a section showing yet another modified radiant energy concentrating means made of silicon to pass infrared (IR) rays;</li><li>Fig. 19 is a section showing a radiant energy transmitting body means, as in Fig. 16a, directing converging light toward a light pipe;</li><li>Fig. 20 is a section showing a radiant energy transmitting means, directing light from as layer-stimulated sample to converge into a spectroscopic analyzen.</li></ul>

0026For a better understanding of the present invention, first, the prior art according to U.S. Patent 4 377 759 will be described with reference to Figs. 1 to 15.

0027As described in U.S. Patent 4,337,759, and referring to Fig. 1, radiant energy transmitting body means 10, in the shape of a cover or dome, has multiple facets or elements as at 11, each facet having an entry face to receive impingement of such radiation, an exit face to pass energy to the exterior of the body, and an internal reflection face angled relative to the entry and exit faces to reflect radiant energy incident on the reflection face toward the exit face. For example, in Figs. 1 and 4<u>d</u>, a selected facet 11 has, in vertical cross section, an entry face 12 made up of stairstepped faces 12<u>a</u> and 12<u>b</u>, an exit face 13 facing the zone of target 15, and an internal reflection face 14. Radiant energy, such as light, is represented by rays 16<u>a</u> and 16<u>b</u> entering the body means 10 at flat face 12<u>a</u> and normal thereto, and passing internally of the facet for reflection by face 14. For this purpose, the face may be silvered at 17. The reflected rays 16<u>c</u> then pass toward and through exit face 13, normal thereto, and directly toward the target zone.

0028The body means 10 may consist of solid transparent material, such as glass or plastic, for example.

0029The multiple facets 11 shown in Fig. 1 may extend annularly about and define a common axis 18; or they may extend in parallel relation (normal to the plane of Fig. 1) at opposite sides of a plane as alternatively represented by 18, and which is normal to the plane of Fig. 1. In either event, corresponding points on the facets define a concave surface, as for example at 21 (defined by the tips 22 of the facets closest the target), and characterized in that radiant energy passing through the exit faces is directed generally toward the target zone. Tips 22 are formed at the intersections of the faces 13 and 14. Surface 21 is parabolic.

0030The series of facets in Fig. 1 is further characterized by the existence of tapered gaps 23 between adjacent faces 24 and 14 of the projecting portions of the facets. Faces 24 are inactive surfaces, i.e., do not pass the radiation. See for example representative rays 25 and 26 in Fig. 1. Ray 25 is redirected by its associated face almost 90° toward the target, near the outer edge 27 of the TIR lens 10. Study of Figs. 1 and 4 will show that angle α (the bend angle of the ray) increases for facets increasing in distance from axis or plane 18; and that angle β (the angularity of face 14 relative to a line or plane parallel to line or plane 18) increases for facets increasing in distance from 18. Also, the entry faces 12 form stairstep patterns.

0031Fig. 1 further shows a Fresnel lens 29 associated with TIR lens or body 10, and located at a mid-portion of the latter; thus Fresnel lens 29, which refracts incident radiant energy toward target 15, is located in the path of rays which are redirected the least, i.e., at the smallest angles, toward the target. Lens 29 may be integral with lens 10, for example.

0032Further, a reflector or mirror surface is shown at 30 spaced from and facing the facets at the target side thereof. Surface 30 is arranged to reflect stray or divergent radiation from the extreme outward facets toward the target. See ray 31 in this regard, and reflection point 31<u>a</u>. This allows target 15 to halve the area exposed to heat loss that it would have without surface 30, since the bottom non-illuminated half could be well insulated.

0033Also shown in Fig. 1 is one form of means to controllably tilt the assembly of lenses 10 and 29 and reflector 30 to cause axis 18 to remain directed toward a relatively moving source of radiation, as for example the sun. In that example, a base plate 32 supports reflector 30 as well as the dome-shaped lens 10 and 29, via extreme outer edge portion 10<u>a</u> of the body means 10. A ring gear 33 supports plate 32, and meshes with spur gear 34. Drive motor 35 rotates gear 34 to controllably rotate ring gear 33, and control unit 36 controls motor 35. Unit 36 is responsive to photocells 37 and 38 in such manner that the photocells remain directed toward the light source. The photocells are suitably carried at 99 by the plate 32, as for example near its periphery.

0034Target 15 may for example comprise a fluid receptacle which is heat conductive, to transmit heat to fluid in the receptacle, as for example water in a pipe.

0035In Figs. 2 and 3, the numerals 100 and 129 designate lenses corresponding to lenses 10 and 29 described above. They are elongated in the direction of arrow 149 and are carried by supports indicated at 150 and 151. V-shaped shroud 152 has edge portions 152a connected to the opposite edges of lens body 100, so that the shroud and lenses define an enclosure. A second and insulative tubular shroud 153 extends within that enclosure, about a tank 154 which has fixed (non rotatable) position. A support for the tank may take the form of legs indicated at 155 and 156, bearings being provided at 157 and 158 to allow tank and shroud rotation about central axis 159, along with the lens assembly. The shroud 153 is cut-away at locations 160 and 161 to allow entry of radiant energy from the lens assembly, to be absorbed by the tank, while heated air is prevented from escaping gap 162 by wibers 163; the enciosure has a reflecting interior surface 152<u>b</u>.

0036Cool liquid, such as water, enters the tank via pipe 164, is heated therein, and discharges into the tank lower end at 164<u>a</u>. Warmed liquid slowly flows at 200 back up the tank, being further heated by contact with the exterior of pipe 164, the liquid leaving the tank at outlet 165. A sacrificial anode 166 in the water 200 is adapted to corrode, electrolytically suppressing any corrosion of the tank itself. Also, a back-up heater 167 in water 200 is supplied with electrical current to heat water in the tank as when solar radiation is blocked or non-existent, as at night. An air-gap may be provided at 162 between shroud 153 and the tank itself. Sun tracking mechanism is indicated at 170, to rotate the assembly to maintain the sun's rays incident normally toward the lenses 100 and 129, i.e., in direction 171 in Fig. 3.

0037In operation, all radiation directed parallel to arrow 171 and striking the lenses 100 and 129 is redirected toward the tank, as facilitated by gaps 160 and 161, to heat the liquid in the tank. Also note windows 162 and 163. Wide angle, i.e., almost 180°, collection of the solar rays is employed, as described above in Fig. 1. The gap walls 153<u>a</u> are reflective, and may have other, curved shapes besides the straight lines shown here, for the purpose of secondary concentration. Stray radiation from the diffuse sources, such as skylight, is absorbed by blackening the surface 153<u>a</u> of shroud 153 and of lens support fin at 130.

0038Various geometric configurations of elements and arrays of elements are possible, wherein various element configurations have the same relative angles of the three active faces, but differing deployments within the transparent means; e.g., the TIR face can be in faceted slots on either side of the body means or on the walls of tunnels within the latter, while the entry faces can be on faceted steps or even on a completely smooth cover surface.

0039In Fig. 4<u>a</u>, tunnel 40 forms TIR face 41, while exit face 42 has stairsteps 42<u>a</u> and 42<u>b</u>. In Fig. 4<u>b</u>, slot 50 is on the entry side of the body means, having TIR face 51 and entry face 54. Exit face 52 has stairsteps 52<u>a</u> and 52<u>b</u>. In Fig. 4<u>c</u>, tunnel 60 forms TIR face 61, and entry face 62 and exit face 64 are on smooth continuous surfaces. However, TIR face 61 must be longer than TIR faces 41 of Fig. 4a or 51 of Fig. 4<u>b</u>, because of the refractive bending of ray 63 by entry face 62. In general, the length of a TIR face relative to facet width 65 is: <ul id="ul0006" list-style="none" compact="compact"><li>TIR LENGTH = cos δ/ (cosη cosη) where η is the incident angle of ray 63<u>a</u> with surface normal 66, δ is the angle of the refracted ray 63<u>b</u> with 66, κ the incident angle of reflected ray 63<u>c</u> with exit surface normal 67, and λ the angle of refracted by 63<u>d</u> with 67. The relationships of these angles are given by Snell's law:</li><li>sinη= n sin δ, and sinλ= n sinκ</li></ul> where n is the index of refraction of the body means material. For contiguous elements to redirect to target all the parallel rays incident upon them, neighboring elements must be relatively positioned everywhere on or above a parabola with the target as its focus and a rim slope equal to half the rim angle (i.e., the redirective bend angle of the outermost elements).

0040In Fig. 4<u>d</u>, "extreme" ray 16<u>c</u> must clear tip 22 of the inward adjacent facet, while the other extreme ray, 16<u>b</u>, must clear top 27 of slot 23. These clearance conditions require that the lens slope angle be greater than or equal to the TIR tilt angle, which is geometrically equivalent to tangent line 22 being on or above said parabola. Note that all of the configurations of Fig. 4 have the same bend angle, and except for Fig. 4<u>c</u>, the same normal entry and exit faces. See for example the elements 311 of the "cover" 310 in fig. 5, above the parabola 321 tangent to the tips 322. See also line 324. Those tips below the parabola, such as for a quarter-circle 325 with the same slope at the rim, would in this stairstep configuration suffer some interelement impingement, about 10% for both cylinders and spheres; but the use of a thin, flexible, inflatable dome for a transparent cover means might be worth such a loss, especially since the untargeted rays would still be redirected to a locus within the cover means, to assist the pressurization by heating the enclosed air. See Fig. 11 for a non-impinging circular configuration. An alternative facet style seeks to minimize such impingement losses by concentrating the rays before they strike the TIR face, which can thereby be smaller to reduce said impingement. Convex and concave entry and exit faces will do this, though with some decrement of the cover's concentration ratio or acceptance angle, which for some applications is far outweighed by bringing the transparent redirecting means even closer to the target.

0041For the smaller bend angles, difficulties are encountered in the narrowness required of the tunnels or slots 23. in Fig. 4<u>d</u> forming the TIR faces of the low bend-angle elements. This can be somewhat alleviated by raising the profile of the transparent means 310 above the parabola 321 to widen the slots and tunnels beyond their minimum widths. Another form of such an alleviation is a backbending exit face, 311 of Fig. 5, so angled that its refractive redirection opposes the redirection of the TIR face, which can thereby have a greater redirective bend angle with a less steep slope, giving wider tunnels or slots.

0042In Fig. 5, note that ray 330 strikes the exit face 11 non-normally, so that ray 330a is bent back toward the target. This enables a wider slot 323 than if the exit face was normal and the TIR face was at a steeper angle. The above-mentioned convex entry face will also widen the slots or tunnels.

0043Another method of widening the slots is the faceted exit face, shown in Fig. 4e. Here slot 70 has been opened until it nearly impinges upon extreme ray 73<u>b</u> Exit face 74 has miniature stairsteps 74<u>a</u> and 74<u>b</u>, re-spectively normal to and parallel to reflected ray 73<u>b</u>. Alternatively, a thin, microstructured series of elements of high refractive index (say n=4) can be embedded in the body means to form more favorably shaped elements. The particular manufacturing method and design application will determine the place of transition to a Fresnel lens, or alternatively to a window, that passes rays to a small parabolic reflector below the target, which is thereby illuminated from a full circle of directions.

0044Another possible configuration would have the outer parts of the redirecting means sending radiant energy to a central target while the inner parts redirected energy to outer targets using only large bend angles throughout. All these configurations are derivatives of the basic method of this invention: upon multiple TIR-transmitting elements, properly placed entry, exit, and TIR faces redirect radiant energy to a predetermined target zone, or into a predetermined target solid angle.

0045Also usable is a cover means (as at 10 or 110) whose focal length can be shorter than any parabolic mirror with concentrations twice as high, but which is free from shading and presents a convex surface with lower aerodynamic drag than the concave parabolic mirror. Its target is near the center of gravity and closer to the ground than that of the parabolic reflector making fixed receiver means easier to design and maintain. Finally, the nearly 100% reflective efficiency of the TIR faces give much greater potential for high efficiencies than does the parabolic mirror.

0046In Figs. 1 and 5, it will be understood that the elements 11 and 311 join together, integrally and continuously, to form a radiant energy transmitting means in the general form of a cover. The latter has an energy entry surface (top surface in Fig. 1, for example) and an exit surface (bottom surface in Fig. 1) lying on opposite sides of the cover. The cover causes radiant energy leaving the exit surface to have a generally different direction than the direction of energy incidence on the entry surface. Also, multiple TIR faces are situated on the surface adjacent slots proximate the exit surface, as referred to above. The entry surface has a faceted stairstep configuration. The exit surface of the cover lies beyond the further from the target than a parabola (see 21 and 321). The cover may be constructed of transparent material, as for example plastic.

0047Fig. 8 schematically shows a means 410 corresponding to the means 10 of Fig. 1 or 310 or Fig. 5, or equivalent. A target zone is shown at 415. A retroreflector means 412 is spaced behind and facing the target zone so as to redirect radiant energy upon the target zone. See ray 413.

0048Fig. 9 schematically shows a radiant energy source means (as for example a light source) at 430 at the target zone. Radiant energy emitted by the source means 430 is redirected by he body means 435 (like 10 or 310) in reverse relation. See ray 436.

0049Figs. 10<u>a</u> and 10<u>b</u> show two variations of a "uni-bend" lens with uniform facets extending annularly about a cylindrical target. In Fig. 10a, the body means 440 bends rays 443 through 90° onto cylindrical target 441. In Fig. 10<u>b</u>, flat body means 445 has identical facets 448 bending rays 447 through 45° upon cylindrical target 446.

0050Fig. 11 shows a structural means 460 enclosing the space 461 behind the exit face of the cover means 459 (like 10 or 310), so that pressurization of the atmosphere of space 461 will hold the flexible cover means in its distended or circular shape, with center of curvature at point 426. See target zone 462, pressurization means such as a pump 463 and ray 464. A thin film 465 adheres to the inside of cover means 459, having miniature sawtooth facets 467 as shown in the insert.

0051Fig. 12a shows a plurality (two for example) of target zones 470 and 471 to receive radiant energy from the transmitting body means 472 (like 10 or 310). Each element 473 redirects energy in a plurality of directions, toward the target zones. Thus, each element 473 may be like element 10 or 310 described above but have a TIR face divided into two sub-faces 474 and 475 at slightly different angles to accomplish the reflection of the two rays 476 and 477, respectively directed by the faces 474 and 475 toward the two target zones.

0052In Fig. 12<u>b</u>, TIR face 453 is the exit face for ray 451; while TIR face 454 is the exit face for ray 452. This symmetrical case of twin 60° bends may be varied to give two different right and left hand bends, with differing division of the incoming radiant energy.

0053In Fig. 13, the cover means 480 (like 10 or 310) has different groups of elements redirecting radiant energy toward different target zones. Thus, the elements at locus 481 direct radiant energy toward target 482; and the elements at locus 483 direct energy toward target 484. See rays 485 and 486.

0054In Fig. 6, cover or body means 510 corresponds to 10 or 310 described above. A secondary radiant energy redirecting means is provided at 520 to intercept the radiant energy from body 510 and to redirect it. See rays 521 with segments 521<u>a</u> falling on body 510; redirected segments 521<u>b</u> falling on body 520; and secondarily redirected segments 521<u>c</u> transmitted by body 520.

0055Fig. 7 shows body 520 in detail, with entry faces 530, exit faces 531, and TIR faces 532. The rays 521<u>c</u> are parallel, in this instance, i.e., collimated, so that means 520 may be regarded as a collimator.

0056The means 550 shown in Fig. 14 is like 10 and 300, except that the exit faces 551 are individually angled relative to radiant energy passing through them, so as to cause refractive redirection of the radiant energy. See beam 552 refracted at face 551. Also in Fig. 14, the exit faces 551 may be considered to refractively redirect radiant energy in partial opposition to the redirection by the TIR faces 553, the latter extending at less steep angles (than in Figs. 1 and 5) so as to widen he slots 554. Note also in Fig. 14 that the entry face is smooth and unfaceted, at 556, and that exit face 551 is parallel to refracted ray 552<u>b</u>, giving the maximum backbend and the lowest possible slope of entry surface 556, which in fact is lower than the parabola 321 or the quarter-circle 325 in Fig. 5.

0057In Fig. 15, the body means 560 is like that at 10 or 310, except that it utilizes the variation index of refraction that varies with the wavelength of the radiant energy, so as to constitute a wavelength separating, radiating energy redirecting, transmitting body means. Two target zones 561 and 562 are shown, and are spaced apart to receive different wavelengths of the wavelength separated, redirected, radiant energy. See incident ray 563 which separates into ray 563a of one wavelength directed toward target 561, and ray 563<u>b</u> of another wavelength directed toward target 562.

0058Also in Fig. 15, either target may be considered as a means to convert radiant energy to electricity. One such means is a photovoltaic cell. Such a device may be located at the target zones in Figs. 1 and 5. In Fig. 15, one target may comprise a photoillumination means receiving visible wavelengths; and the other target may comprise a thermal receiver receiving invisible wavelengths at zone 561.

0059When a source of radiant energy is placed in zone 562, the visible wavelength rays will follow the reverse path of rays 563, i.e., be collimated, while the invisible longer wavelength heat rays will abe diverged more outward from the visible beam, so that spotlights on actors will not subject them to a heat toad several times greater than that of the visible radiation.

0060Certain aspects of Figs. 1-15 were also discussed in US patent 4,337,759.

0061In the following, a detailed description of the present invention will be made.

0062In Figs. 16a, 16b and 16c, the bodies 650, 660 and 670 are closely similar to body 740 shown and described in Fig. 17. The angularities of the annular facets are slightly varied, so that the body 660 produces collimated light rays 664; body 650 produces converging light rays at 654; and a body 670 produces diverging light rays 674. The light source in each case is shown at 680. In each case, the top surface 659, 669, and 679 of the lens is circularly curved in the section shown, or spherically curved for an annular lens.

0063In Fig. 17, the axis of the annular, radiant energy transmitting body 740 appears at 751. The body has multiple annular facets 742 to 746 which are generally concentrically arranged, but having tips 742<u>d</u> to 746<u>d</u> progressively closer to plane 750 normal to axis 751. Face 742<u>a</u> of facet 742 is convex toward face 742<u>b</u>; and face 742<u>b</u> is concave toward face 742<u>a</u> in the section shown. This relationship obtains for other facets, as shown. A light-emitting diode (LED) 758 is located at the intersection of plane 750 with axis 751 and emits light rays toward the body 740. Ray 753 passes through face 742<u>a</u>, is refracted toward TIR face 742<u>b</u> and is reflected toward and passes through upper flat face 748. See also ray 752 passing through face 743<u>a</u>, reflecting at TIR face 743<u>b</u>, and passing upwardly beyond face 748. The transverse width of the body 740 may be from 0.12 to one inch, for example, and the transparent body 740 may consist of molded plastic material. A refractive section without facets appears at 719. Smaller ratios of lens diameter to LED size may have outermost facets large, and successively inward facets smaller, in order to have a higher lens profile and better collimation curved facets are necessary for.

0064In Fig. 18, the radiant energy transmitting body 760 may have the same general construction as shown in Fig. 17. The lens body 760 consists of silicon, or a similar material, for passing infrared rays, but blocking visible light rays, while transmitting infrared rays. An arc lamp radiant energy source is shown at 764, at the same position as the LED in Fig.17. A reflector surface 765 may be employed to extend in plane 766 corresponding to plane 750 in Fig. 17 with a parabolic section 762. The infrared rays emanating at 767 are typically collimated but may be divergent or convergent, as in Figs. 16a and 16c. Note that unfaceted central section 770 refracts rays, as shown. The arc light source at 764 may be produced by anode and cathode elements 764<u>a</u> and 764<u>b</u>. Top exit surface 759 is circularly curved in the section shown; but the lens may have external, stairstep faceting. Protective transparent envelope 769 keeps outside air away from the arc.

0065In Fig. 19, the body means 780 may have the same or similar construction as that of Fig. 16a, for producing and directing convergent light at 781 into the entrance end 782 of a light pipe 783. The lens has an upwardly convex arcuate upper exit surface or face 785, entrance faces 786, and TIR faces 787. Faces 786 and 787 taper downwardly toward plane 790, corresponding to plane 710 in Fig. 17. A central light source 788 is positioned in the manner of the LED in Fig. 17. A planar back mirror 789 extends in plane 790 corresponding to plane 710 and faces upwardly. This device may input up to 80% of the light into pipe 783, rather than 10% of the light as via a conventional ellipsoidal reflector.

0066In Fig. 20, lens body is the same as that of Fig. 17, except that the central refractive means has been replaced by microscope objective 854, which can slide axially inside the lens to focus on sample 851. Characteristic diffuse (i.e., in all directions) emission 856 from sample 851 is collected by lens 850 and focused on analyzer entrance slit 852. Collimated laser bean 855 is reflected by mirror 853 into objective 854 and focused on sample 851. Mirror 853 is removable in order to use microscope objective 854 to view sample 851 and exactly adjust its position. Lens body 850 could extend downward below sample 851 to collect even more of the diffuse emission. Sample 851 may be a glass capillary containing a gas or liquid, a gold hemisphere coated with a sample substance, an integrated circuit on a production line (checking material composition or contamination), or a biological tissue sample.