Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/09—Other methods of shaping glass by fusing powdered glass in a shaping mould
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/30—Arrangements for concentrating solar-rays for solar heat collectors with lenses
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
  • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
  • G02B19/0009—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only
  • G02B19/0014—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only at least one surface having optical power
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
  • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
  • G02B19/0038—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light
  • G02B19/0042—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with ambient light for use with direct solar radiation
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/0087—Simple or compound lenses with index gradient
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/40—Solar thermal energy, e.g. solar towers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P80/00—Climate change mitigation technologies for sector-wide applications
  • Y02P80/20—Climate change mitigation technologies for sector-wide applications using renewable energy

Definitions

• the present invention relates generally to devices for directing radiant energy, and more particularly to transmissive light concentration devices and compact opti- cal systems utilizing optically refractive media having a gradient in the optical density or index of refraction in three dimensions.
• the gradient best suited to achieve this pur ⁇ pose is described as having the greater index values along the axis of the generally cylindrical device with the values therefor falling away from this axis.
• This is known as a purely radial gradient.
• Fig. 3 also teaches the combination of a nonhomogeneous refractive media and a reflective wall. Two media are shown, but an infinite number are possible.
• the media increase in optical density as a function of the radius of the device.
• the stated purpose for utilizing such a distribution is to reduce the cost of the overall device; that is, the innermost region might be filled with water. See, e.g.. Col.
• a diluent into a shaped polymeric matrix to form a continuous gradi- ent in refractive index in a direction perpendicular to the optical axis thereof.
• the diluent and the polymeric material have different refractive indices.
• an angularly symmetric, radial gradient of re ⁇ fractive index substantially proportional to the radial distance perpendicular to the optical axis may be formed by diffusion of a diluent having lower index of refraction than the plastic matrix material into the matrix from the central core thereof.
• inward diffusion of a diluent external to a plastic rod is required.
• N N 0 (l - ar 2 ) was generated in a glass rod, where r is the distance from the center in the radial direction, a is a positive constant, and N 0 is the refractive index at the center of a cross section of the glass body perpendicular to the central axis thereof.
• optical axis For the purpose of the present specification, we define the term "optical axis" to mean an imaginary straight line which extends internally through the refrac- tive material of the subject invention and which passes through both the entrance and exit surfaces of this mate ⁇ rial which are adapted for the passage of light. Although there may be more than one optical axis for a chosen embo ⁇ diment of the invention, in general, the optical axis will be uniquely defined by the geometrical symmetry of the material. In either event, changes in the index of re ⁇ fraction of the refractive material will be defined rela ⁇ tive to the optical axis.
• bidirectional gradient to refer to a gradient in the index of refrac ⁇ tion that occurs along each of two directions, usually mutually orthogonal.
• light is defined as that electromagnetic radiation in the frequency spectrum rang ⁇ ing from infra-red through visible to ultraviolet.
• transmitting light concentrating and/or directing devices having bidirectionally varying indices of refraction or devices having indices of refraction varying in three dimensions having substantial thickness in the direction of variation of refractive index.
• Still another object of the present invention is to provide a non-tracking transmissive solar energy collector having a broad acceptance angle.
• Another object of our invention is to provide a transmissive light image reducer or enlarger.
• Yet another object of the present invention is to provide a process for the fabrication of monolithic glass articles having a significant bidirectional gradient in index of refraction and for the fabrication of glass arti ⁇ cles having a varying index of refraction in three dimen ⁇ sions.
• Another object of our invention is to generate simi- lar transmission characteristics in a single, integral lens to those provided by at least two individual lenses cooperating as a compound lens.
• light directing devices which include a transmissive refrac ⁇ tive material having a bidirectional gradient in the re- fractive index thereof.
• Examples of such light directing devices include imaging and non-imaging devices, such as lenses, concentrators, and the like.
• the light directing devices of the invention are characterized by a macro-gradient in index of refraction.
• macro-gradient or significant gradient, is meant a change index of refraction of at least about 0.1.
• Fur ⁇ ther, these devices may possess a gradient in index of refraction of greater than 0.3 and even as high as 0.5, values unheard of in conventional prior art glass articles having a gradient in index of refraction.
• the light directing devices of the invention are further characterized by a large geometry, or substantial thickness, with devices as fabricated having a dimension of at least about 5 mm in the direction perpendicular to the optic axis.
• a non-tracking transmission light concentrator device of this invention includes a transmissive refractive material having gener ⁇ ally flat entrance and exit surfaces, and having a bidi- rectional gradient in the refractive index thereof, the gradient generally changing in a direction perpendicular to an optical axis and generally changing in a direction parallel thereto in the direction from the entrance sur- face to the exit surface of the refractive medium.
• the refractive material might include reflective boundaries as side walls so contoured that energy incident on the entrance surface and directed thereto by the refractive material is substantially di- rected to the exit surface of the refractive material.
• the reflective boundaries might be opposing surfaces symmetrically disposed about the optical axis extending between the entrance surface and the exit sur ⁇ face and generally contoured such that the refractive material defines a device wherein the entrance surface has a larger area than the exit surface.
• the non- tracking transmission light concentrator device of this invention includes a transmissive refractive material having generally flat entrance and exit surfaces, and having a bidirectional gradient in the refractive index thereof, the gradient generally decreasing in a direction perpendicular to an optical axis and generally increasing in a direction parallel thereto in the direction from the entrance surface to the exit surface of the refractive medium.
• the image reduc ⁇ ing or enlarging device hereof includes a transmissive refractive material having generally flat entrance and exit surfaces, and having a bidirectional gradient in the refractive index thereof, the gradient generally decreas ⁇ ing or increasing in a direction perpendicular to an opti ⁇ cal axis, respectively, and generally either increasing or decreasing in a direction parallel thereto in the direc ⁇ tion from the entrance surface to the exit surface of the refractive medium, respectively, from the entrance surface to the position of approximately one-half of the length of the optical axis, and further having substantially the opposite variation of the index of refraction both along the optical axis and radially away therefrom from the approximate midpoint thereof to the exit surface of the device.
• the refractive material might have a substantially constant index of refraction along the optical axis itself.
• the process for preparing an article having a bidirectionally graded index of refraction hereof includes the steps of preparing a series of powdered glass samples having decreasing indices of refraction and similar coefficients of expansion in vitrified form, placing a portion of the powdered glass sample having the highest or lowest index of refraction in the bottom region of a crucible having a chosen shape and having further a generally cylindrical cross section to a chosen height, mechanically compacting the sample, forming an annular region between the wall of the crucible and the central volume thereof beginning above the layer of pow- dered glass sample having the highest or lowest index of refraction by using a cylindrical tube having a thin wall and a chosen outside diameter, forming successive layers of the powdered glass samples each having a chosen height in the annular region formed and mechanically compacting each layer before the next layer is placed above it, each layer being composed of a powdered glass having an index of refraction lower or higher,
• the glass powders having intermediate indices of refraction result from mixtures of the highest and the lowest index of refraction powdered glass materi ⁇ als.
• Benefits and advantages of the present invention include the ability to provide non-tracking transmissive light concentrators and directors having greater concen ⁇ tration and smaller overall dimensions than similar exist ⁇ ing devices, and the ability to design single lenses with- out interfaces which accomplish the function of present compound lenses.
• the process hereof provides monolithic glass articles having significant changes in index of refraction.
• Figure 1 shows a trace derived from a digitized cam ⁇ era image of HeNe laser radiation passing through a sample of glass fabricated according to the process of the pres ⁇ ent invention ( Figure la) compared with a similarly de- rived image of HeNe laser radiation passing through a homogeneous sample of glass ( Figure lb).
• Figure 2 shows a graphical representation of the functional form of the algorithm chosen to illustrate the dependence of the index of refraction on the distance from the axis of symmetry and along this axis of a combination cylindrical/conical cross section transmissive concentra ⁇ tor shape at five arbitrarily chosen locations along this axis.
• Figure 2a shows the location of the five chosen points along the axis of the continuously graded chosen concentrator shape
• Figure 2b shows the values of the index of refraction at these locations as. a function of radial distance from the axis of symmetry of the lens which is also the optical axis thereof.
• This algorithm was employed in some of the calculated curves which follow in order to assist in the understanding of the present inven ⁇ tion, but other functional forms may provide improved concentrator characteristics.
• Figures 3a-c show a computer generated comparison of the passage of light through a series of conical/cylindri- cal cross section refractive elements having identical physical dimensions and hereafter referred to as conical/- cylindrical elements.
• Figure 3a describes a refractive element constructed of material having a homogeneous index of refraction.
• Figure 3b describes a refractive element having a purely radial gradient in its index of refrac ⁇ tion
• Figure 3c describes an identically shaped ele ⁇ ment having a bidirectional index of refraction according to the algorithm illustrated in Figure 2 hereinabove for incident light at 10°.
• the calculated gains are 1.3 ⁇ 0.1, 4.1 ⁇ 0.1, and 6.9 ⁇ 0.1, respectively.
• Figures 4a-e show a computer generated comparison among a group of refractive elements having parabolic cross section, while Figures 4f-g show examples of the gradient profile manifest in particular three-dimensional shapes.
• Figure 4a describes a refractive element having a homogeneous index of refraction.
• Figure 4b describes a similarly shaped refractive element having a purely radial distribution of indices of refraction, and
• Figure 4c de ⁇ scribes a refractive element having a bidirectional index of refraction which varies according to the algorithm depicted in Figure 2 hereof for incident light at 10".
• the calculated gains are 2.9 ⁇ 0.1, 4.1 ⁇ 0.1, and 6.9 ⁇ 0.1, respectively.
• Figure 4d illustrates the effect of slightly altering the shape of the reflective boundary walls of the parabolic shaped element for a similar dis ⁇ tribution of refractive indices as that of the refractive element of Figure 4c.
• the gain increases to 8.5 ⁇ 0.1.
• Figure 4e shows the effect of increasing the index of refraction for a homogeneous index of refraction refrac ⁇ tive element having parabolic reflective boundary walls. The gain increases as would be expected (in fact to 3.9 ⁇ 0.1).
• Figure 4f shows the gradient profile of any of the elements of Figures 4a-e manifest in a 3-D conical shape.
• Figure 4g shows the gradient profile of any of the ele ⁇ ments of Figures 4a-e extended into a trough shape.
• Figure 5a shows the computer generated response of a refractive element having conical cross section and a compound bidirectional index of refraction according to the algorithm depicted in Figure 2 hereof which reverses as illustrated in Figure 5b for normally incident light.
• the compound refractive element behaves as an image reduc ⁇ er with a calculated gain of 7.0 ⁇ 0.1.
• Figure 6a and 6b show a computer generated comparison between two refractive elements having cylindrical cross section for the purpose of identifying the effect of the longitudinal gradient in the refractive index.
• Figure 6a describes a refractive element having a purely radical gradient in index of refraction
• Figure 6b describes a similarly shaped refractive element having a bidirec ⁇ tional distribution of index of refraction.
• the gradients in radial index of refraction for the two Figures were chosen to be identical.
• the present invention teaches a process for the fabrication of glass light directing or transmitting devices having a chosen gradient in index of refraction and articles having a chosen gradient index of refraction either bidirectionally (radially and longitudinally rela ⁇ tive to an optical axis) or in three dimensions.
• Such articles have numerous uses in the optics, optical fiber and solar technology industries for the purposes of de ⁇ signing compound lens systems using a single, integral lens, coupling light into fibers and for concentrating and directing light from a source having significant angular variation to an energy collecting and/or conversion de ⁇ vices such as a photovoltaic cell, to name but a few ap ⁇ plications for the devices of the present invention.
• Figure la illustrates a trace derived from a digitized camera image of HeNe laser radiation passing through a sample of glass fabricated according to the process of the present invention.
• Light 2_H from a helium neon laser is curved 12. as it passes through a generally rectangular refractive glass element shown in cross section and having a bidirectional gradient (radial ⁇ ly and longitudinally) in its refractive index.
• the direc- tion of travel of light ray 12. inside of the medium may be controlled independently of the nature of the surface of the refractive material. Exiting light .30. travels in a straight line.
• the functional form of the index of refraction inves ⁇ tigated as an example of the desirable characteristics of refractive devices having a bidirectional gradient in their index of refraction is:
• n a - b*[x/B(z)] 2 *[l - z/D(tot)], (1)
• Equation 1 provides a three-dimensional represen- tation of the index of refraction.
• Equation 1 describes the variation of index of refraction of a cross section or plane of symmetry of the trough perpendicular to what would generally be the long axis thereof.
• Figure 2 shows a graphical representation of the functional form of the algorithm described in Equation 1 for a combination cylindrical/conical transmissive concen ⁇ trator shape illustrated in a cross sectional view at five points along the axis of symmetry thereof.
• Figure 2a shows the location of the five chosen points along the optical axis of the chosen concentrator shape, while
• Figure 2b shows the values of the index of refraction at these loca ⁇ tions as a function of radial distance from the optical axis of the lens.
• the optical axis may be the axis of symmetry of a generally cylindri ⁇ cal lens, the axis of symmetry of a trough or simply an axis chosen to define the path of a ray of light through a refractive element.
• the displayed algorithm was employed in all of the calculated curves which follow in order to assist in the understanding of the present invention, but other functional forms may provide other desired concen- trator and compound lens characteristics.
• Equation 1 the follow ⁇ ing specific example of the fabrication of a transmitting light concentrating refractive element having significant dimensions and approximating the variation in index of refraction illustrated in Equation 1 is presented as a further illustration thereof.
• the same proce ⁇ dure is applicable to the fabrication of integral lenses having the properties of compound lens systems composed of " multiple lenses.
• bidirectional gradient refractive index having a controlled profile in a monolithic sample of glass two glass compositions possessing distinct charac ⁇ teristics were obtained. Each glass was in frit form ground to 350 grit size.
• the first glass a lead-borate glass, was comprised principally of the following oxides: lead oxide, boron oxide, and aluminum oxide.
• the glass contained small amounts of silicon, calcium and sodium oxides, along with additives used as fining agents. This glass was purchased from Specialty Glass, Inc. (Oldsmar, FL) .
• the refractive index was 1.97, the softening te per- ature was 350° C, and the coefficient of thermal expansion was 102 x 10" "7 cm/cm/ ⁇ C.
• the second glass a sodium boro ⁇ silicate glass
• the second glass was comprised principally of the following oxides: silicon dioxide, boron oxide, sodium oxide, alumi ⁇ num oxide, and potassium oxide.
• the second glass also contained small amounts of calcium and lead oxides.
• This glass was similarly purchased from Specialty Glass, Inc.
• the refractive index of this glass was 1.57, the softening temperature was 950° C, and the coefficient of thermal expansion was 97 x 10 ""7 cm/cm/ ⁇ C.
• the powdered glasses were mixed by weight and labeled as follows:
• Approximately 1 ml of the #1 glass powder was placed in the bottom of a generally cylindrical platinum/gold alloy crucible having a 25 ml capacity and having a 3 cm top diameter, a 2 cm bottom diameter, and a 4 cm height.
• the powder was mechanically compressed using a tamp.
• a thin wall cylindrical sleeve having an approximate outside diameter of 2 cm was then placed in the crucible such that it rested on the layer of compacted glass #1 and such that its cylindrical axis was approximately colinear with that of the crucible.
• the sleeve was then surrounded with successive layers of about 0.5 cc each of consecutively numbered glass mixtures, each mixture being mechanically compacted to an approximately 0.4 cm height before the next higher numbered glass mixture was added.
• the cruci- ble was about filled when the #10 glass powder was added and compacted. The sleeve was then removed and the center region was filled with the #1 glass powder until its com ⁇ pacted height reached the level of the #10 powder.
• the refractive index of the glass powders would be expected to vary according to the percentages of the component glasses so that a bidirectional gradient in index of refraction would be expected upon fusing the compound mixture pro ⁇ quizd thereby.
• the final gradient should vary from a high of 1.97 at the axis to lower values at the exterior of the sample and increase from the top of the sample to the bottom thereof.
• the crucible was placed in an electric kiln and slowly heated to 1000°C to permit controlled release of gases adsorbed on the surface of the glass powders.
• the sample was kept at this temperature for about 10 hours. Longer or shorter time periods were employed depending on the overall size of the crucible employed, longer time periods being used for larger samples.
• the temperature was reduced at a sufficiently slow rate to permit annealing of all of the glasses used. Typically, the cooling process was achieved in a 10 hour period. After the glass sample reached room temperature, it was removed from the crucible. Separation of the glass from the crucible walls was readily achieved with only minor cracking near the top of the sample. This region was re ⁇ moved by grinding. Flat entrance and exit surfaces (top and bottom of the sample) were also produced by polishing. The size of the glass sample, after polishing, was about 2.5 cm thick and about 2.5 cm top diameter and 2.0 cm bottom diameter.
• the number of layers of frit in a particular applica ⁇ tion depend on the resistance to glass fusion and on the change (gradient) in index of refraction desired. Where two compositions have a tendency to separate or where a larger gradient is desired, then more layers of different refractive index will be required.
• the thinnest articles, perpendicular to the optic axis, that can be fabricated by frit fusion are estimated to be about 5 mm.
• Number Arr. is the number of light rays which ac ⁇ tually reach the exit surface, there being a significant number which are reflected out of the refractive element depending on the angle of incidence of the light rays. It should be mentioned that all calculated gains reported herein are for trough geometries. Gains will be higher for cylindrically symmetric devices. Therefore, relative gains will be more pronounced for such systems.
• the algorithm used to generate the bidirectional gradient has not been optimized nor has the range of indices and the size and shape of the concentrator or compound lens been investigated for optimal performance.
• Various consi ⁇ derations need be taken into account in the design of a concentrator or a compound lens such as the desired spot size and reduction in the amount of absorption in the transmission process, to identify two.
• the shape of the refractive element is not important for small incident angles since few rays impinge upon the boundaries at sharp angles.
• reflec- tive coatings are not necessary for small incident angles. Indeed, reflective coatings may not be necessary in most cases. As long as the angle for total internal reflection is not exceeded, few rays are lost from the refractive element.
• our invention may be used in co ⁇ operation with curved entrance and exit surfaces to achieve yet other valuable characteristics.
• Figures 3a-c show a computer generated comparison of the passage of light through a series of conical/cylindri ⁇ cal cross section refractive elements 2A-
• Figure 3a de ⁇ scribes a refractive element constructed of material hav ⁇ ing a homogeneous index of refraction
• Figure 3b describes a refractive element having a purely radial gradient in its index of refraction
• Figure 3c describes a simi ⁇ larly shaped element having a bidirectional index of re ⁇ fraction according to the algorithm illustrated in Figure 2 hereinabove for incident light at 10°.
• the size of the exit cell 40 The size of the exit cell 40.
• Figures 4a-e show a computer generated comparison among a group of refractive elements .26. having parabolic cross section.
• Figure 4a describes a refractive element having a homogeneous index of refraction.
• Figure 4b de-scribes a similarly shaped refractive element having a purely radial distribution of indices of refraction, and
• Figure 4c describes a refractive element having a bidirec ⁇ tional index of refraction which varies according to the algorithm depicted in Figure 2 hereof for incident light at 10°.
• the calculated gains are 2.9 ⁇ 0.1, 4.1 ⁇ 0.1, and 6.9 ⁇ 0.1, respectively.
• Figure 4d illustrates the effect of slightly altering the shape of the reflective boundary walls of the parabolic cross section element for a similar distribution of refractive indices as that of the refractive element of Figure 4c.
• the gain increases to 8.5 ⁇ 0.1.
• Figure 4e shows the effect of increasing the index of refraction for a homogeneous index of refraction refractive element having parabolic reflective boundary walls. The gain increases as would be expected (in fact to 3.9 ⁇ 0.1). Three rays escaped from the device shown in Figure 4a and none from the other devices of Figure 4.
• Figures 4f-g depict the gradient profile of any of Figures 4a-e manifest in three dimensions.
• Figure 4f shows the 3-D conically-shaped object obtained by rotating the gradient profile about the vertical axis.
• Figure 4g shows the 3-D trough-shaped object obtained by translating the gradient profile along an axis perpendicular thereto.
• Figure 5a shows the computer generated response of a refractive element 28 having a conical cross section and a compound bidirectional index of refraction according to the algorithm depicted in Figure 2 hereof which reverses as illustrated in Figure 5b for normally incident light.
• the compound refractive element behaves as an image reduc- er with a calculated gain of 7.0 ⁇ 0.1.
• Figure 6a and 6b show a computer generated comparison between two refractive elements 2 L having cylindrical cross section for the purpose of identifying the effect of the longitudinal gradient in the refractive index.
• Figure 6a describes a refractive element having a purely radial gradient in index of refraction
• Figure 6b describes a similarly shaped refractive element having a bidirec ⁇ tional distribution of index of refraction.
• the gradients in radial index of refraction for the two Figures were chosen to be identical and to have the functional form:
• n A(z) + B(z)*x 2 , (3)
• a and B are functions of z, the distance along the axis of the cylinder, and x is the radius measured there ⁇ from.
• the size of the focus for the purely radial index of refraction is approximately 0.14 in. in diameter, while the exit surface 4J is about 0.91 in. in diameter, yield ⁇ ing a shift in the focus spot of 0.77 in.
• the same para- meters for the bidirectional gradient are 0.18 in. and 0.77 in., respectively, yielding a shift in the focus spot of 0.59 in.
• the use of a gradient in refractive index along the axis produces two effects. First, the spot size increases slightly.
• the shift in spot focus is significantly reduced when the angle of incidence for the incoming light rays is changed from +10° to -10°.
• the gains for the two elements are 5.19 ⁇ 0.1 and 6.17 ⁇ 0.1, respectivel .
• the light directing devices of the invention have numerous uses in, for example, the optics, optical fiber and solar technology industries for the purposes of designing com ⁇ pound lens systems using a single, integral lens, coupling light into fibers and for concentrating and directing light from a source having a significant angular variation to an energy collecting and/or conversion devices such as a photovoltaic cell.

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• 1988
  • 1988-08-09 EP EP19880907902 patent/EP0354927A4/en not_active Ceased
  • 1988-08-09 JP JP63507148A patent/JPH01503576A/ja active Pending
  • 1988-08-09 WO PCT/US1988/002714 patent/WO1989001640A1/en not_active Application Discontinuation
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