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WO1992008254A1 - Method for the fabrication of lenses with a variable refraction index - Google Patents

Method for the fabrication of lenses with a variable refraction index Download PDF

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Publication number
WO1992008254A1
WO1992008254A1 PCT/EP1991/001981 EP9101981W WO9208254A1 WO 1992008254 A1 WO1992008254 A1 WO 1992008254A1 EP 9101981 W EP9101981 W EP 9101981W WO 9208254 A1 WO9208254 A1 WO 9208254A1
Authority
WO
WIPO (PCT)
Prior art keywords
refraction index
lens
lenses
produced
thread
Prior art date
Application number
PCT/EP1991/001981
Other languages
French (fr)
Inventor
Gerhard Maier
David Harrison
Masahiro Fujimoto
Original Assignee
Thomson Consumer Electronics S.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thomson Consumer Electronics S.A. filed Critical Thomson Consumer Electronics S.A.
Priority to JP3516866A priority Critical patent/JPH06502052A/en
Priority to DE69103764T priority patent/DE69103764T2/en
Priority to EP91918271A priority patent/EP0555262B1/en
Priority to US08/080,390 priority patent/US5421848A/en
Priority claimed from AU87835/91A external-priority patent/AU630329B3/en
Publication of WO1992008254A1 publication Critical patent/WO1992008254A1/en
Priority to HK13797A priority patent/HK13797A/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/23—Combinations of reflecting surfaces with refracting or diffracting devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/02—Refracting or diffracting devices, e.g. lens, prism

Definitions

  • the invention relates to a method for the fabrication of three-dimensional lenses with a variable refraction index.
  • Lenses with a variable refraction index such as a Luneburg lens or a Eaton-Lippmann lens
  • a variable refraction index such as a Luneburg lens or a Eaton-Lippmann lens
  • lenses with variable refraction indexes can be used as radar reflectors or, as is known from E. F. Buckley; "Stepped-Index Luneburg Lenses"; Electronic Design, ApriL, 13, 1960, as part of an antenna system.
  • the Layers for the fabrication of Luneburg and Eaton-Lippmann lenses can be produced by mixed dielectrics.
  • a mixed dielectric can be obtained by mixing expanded particles selected from the group consisting of expanded polystorols, expanded polyethylenes, expanded polyuret hanes, glass balloons and silica balloons, with metal-coated particles consisting of said expanded particles, surfaces of which have been coated with a thin film selected from the group of chromium, aluminium, copper, nickel, gold, silver, and magnesium in proper proportions to obtain a desired dielectric constant then forming the same to the desired shape by the use of a binder.
  • the method according to the invention allows to produce three-dimensional lenses with a variable refraction index n by wrapping a material with a given refraction index, e.g such as the known materials from US 4 288 337, into the final shape of the lens to be produced.
  • a material with a given refraction index e.g such as the known materials from US 4 288 337
  • the method for the fabrication can be executed more easiIy.
  • Fig 1 shows a known Luneburg lens radar reflector
  • Fig 2 shows a known Luneburg lens antenna
  • Fig 3 shows a preferred embodiment
  • Fig 4a, b show possible shapes of thread used.
  • the lenses to be produced are able to refract electromagnetic waves, preferably microwaves.
  • the material with a given refraction index n is a dielectric material and the refraction index n is given by the expression
  • Fig. 1 shows a three-dimensional Luneburg lens 10, which works as radar reflector and as is state of the art.
  • An incoming wave 11 is focussed by the lens 10 in such a way that the wave is focussed on a focus point 12.
  • the wave is reflected by a reflector 13, whereby the reflected wave 14 is generated, which is led by the lens 10 in such a way, that it leaves the lens 10 in the same direction as the incoming wave 11 came from.
  • a is the radius of the lens
  • r/a 1.0 at the outer surface of the lens.
  • Fig. 2 shows another application of the Luneburg lens 10.
  • an incoming wave such as 11a is led to a first focus point 12a and received by a first feeder horn 20a.
  • incoming waves 11b and 11c are led to focus points 12b, 12c and received by feeder horns 20 b, 20c respectively.
  • the signals received by the feeder horns 20a, 20b, 20c are led to not shown receivers.
  • system according to fig. 2 can also work as transmitter antenna, if transmitters are connected to the feeder horns 20a, 20b, 20c.
  • the three-dimensional lens 10 is produced by wrapping a dielectric material, preferably shaped as a thread. This is in principle shown in fig.3.
  • the effective relative dielectric constant may be varied by a variation of the relative dielectric constant E of the thread. This could be achieved e.g. by a variation of the chemical composition or by a variation of the density of said thread with length. A variation of density with length could be achieved e.g. by a variation of pressure, proceeded by a press arranged before the lens 10' to be produced.
  • a crimped thread e.g. like it is shown in fig. 4a or 4b, which might be stretched by a variation of a stretching force used.
  • the dielectric constant of the thread may also be varied along the length with the aid of a metallic paint.
  • a low density dielectric thread of constant dielectric constant is used and as it is wrapped into the shape of the lens to be produced small areas of the thread are painted at a separation necessary to give the correct dielectric constant profile. That means for a desired value of the effective refraction index the thread used is painted with a paint, which may be metallic. Thickness, density or/a n d intensity of this paint may be varied. This is a simple method and will result in a relatively light lens.
  • the material with the given refraction index may have any other appropriate shape, e.g. Like a strip, ribbon, or the like
  • the lens to be produced may be able to refract other electromagnetic waves, such as visible or infrared light.
  • other electromagnetic waves such as visible or infrared light.
  • lenses with non- spherical shapes may be produced,
  • the lens to be produced may have any desired relation
  • the wrapping process may start at the surface of a core, which itself might have a variation of the refraction index and might be located around the center point,
  • a bonding agent may be used, which e.g. might be wrapped with the dielectric thread and when cured at an elevated temperature forms a more solid lens. of course, it might also be possible to dip the lens to be produced into an appropriate bonding agent during or/and after the wrapping process.
  • the invention presents a method for the fabrication or production of three-dimensional lenses with a variable effective refraction index by wrapping a material with a given refraction index, which may be constant or may vary with length. It is preferred, that said material has the shape of a thread, which might be cylindrical.
  • the preferred shapes of the lens to be produced are spherical or semi-spherical. The latter one can be achieved by an appropriate wrapping process or by cutting the spherical shape.

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  • Aerials With Secondary Devices (AREA)

Abstract

The invention presents a method for the fabrication or production of three-dimensional lenses with a variable refraction index by wrapping a material with a given refraction index. It is preferred, that this material has the shape of a thread, which might be cylindrical. The preferred shape of the lens to be produced is spherical or semi-spherical, which can be achieved by an appropiate wrapping process or by cutting the spherical shape. By the inventive method it is possible to produce the said lenses with a smooth varying of the refraction index. It is preferred to use the produced lenses as part of a microwave antenna system.

Description

Method for the Fabrication of Lenses with a variable Refraction Index
The invention relates to a method for the fabrication of three-dimensional lenses with a variable refraction index.
Lenses with a variable refraction index, such as a Luneburg lens or a Eaton-Lippmann lens, are well known. It is also known, e.g. from US 4 288 337, that lenses with variable refraction indexes can be used as radar reflectors or, as is known from E. F. Buckley; "Stepped-Index Luneburg Lenses"; Electronic Design, ApriL, 13, 1960, as part of an antenna system.
As Buckley has described in said article, it is a known method for the fabrication of Luneburg lenses to use a hemispheri- cal-shell construction with a given number of Layers.
According to said US patent the Layers for the fabrication of Luneburg and Eaton-Lippmann lenses can be produced by mixed dielectrics. Such a mixed dielectric can be obtained by mixing expanded particles selected from the group consisting of expanded polystorols, expanded polyethylenes, expanded polyuret hanes, glass balloons and silica balloons, with metal-coated particles consisting of said expanded particles, surfaces of which have been coated with a thin film selected from the group of chromium, aluminium, copper, nickel, gold, silver, and magnesium in proper proportions to obtain a desired dielectric constant then forming the same to the desired shape by the use of a binder. From the article "A multiple-beam multiple-frequency spherical Lens Antenna System providing hemispherical Coverage" of M. A. Mitchel et al.; 6. International Conference on Antennas and Propagation (ICAP) 1989, Part 1, pp. 394 - 398 it is known that the relative dielectric constant, and by this the refraction index, of a dielectric material, such as polysterene, can be modified by a variation of density of said material.
Thereby hemisperical shells with given refraction indexes may be produced.
From US 3 307 196 a method is known, which allows the production of a two-dimensional dielectric lens, such as a disk, by winding a ribbon, shut or strip type of module.
In the US patent 3 307 196 it is proposed to fabricate a three-dimensional dielectric lens by the individual preparation of wound disks, which are superposed upon one another. The superposed disks are of successively different diameters and dielec-tric profile and could be formed, starting with individual substantially strip or ribbon modules, by cutting successively different lengths away from the high dielectric constant ends of said different strips, and then rewinding the resultant successively different length strips.
There are two disadvantages in the known methods for the fabrication of three-dimensional lenses. It is either possible just to approximate the variation of the refractive index required, which is dependent on the dielectric constant. Or it is necessary to carry out a large number of steps. That means no easy and practical method for smoothly varying the refractive index has been achieved.
By using shells with different dielectric constants and thereby with different refraction indexes, reflection losses occur by which power is reflected from the dielectric boundaries. It is an object of the invention, to present an easy method for the fabrication of lenses with a variable refraction index, which overcomes the deficiencies of the prior art.
This can be realized by a method according to claim 1.
The method according to the invention allows to produce three-dimensional lenses with a variable refraction index n by wrapping a material with a given refraction index, e.g such as the known materials from US 4 288 337, into the final shape of the lens to be produced.
It is an advantage of the invention to present a method for the fabrication with a reduced number of steps.
It is a further advantage of the invention to produce lenses with a better aperture efficiency by avoiding surface waves, which are set up at the spherical boundaries, and by achieving a more exact phase of the colliminated rays at the feed points, which makes the lens less frequency dependent.
If the material with the given refraction index is shaped as a thread, the method for the fabrication can be executed more easiIy.
The present invention will be better understood with the aid of the following description and accompanying drawings, wherein
Fig 1 shows a known Luneburg lens radar reflector,
Fig 2 shows a known Luneburg lens antenna,
Fig 3, shows a preferred embodiment,
Fig 4a, b show possible shapes of thread used.
Prior to the detailed description it should be mentioned, that in the preferred embodiment the lenses to be produced are able to refract electromagnetic waves, preferably microwaves. In this case the material with a given refraction index n is a dielectric material and the refraction index n is given by the expression
E = n2,
where E is the relative dielectric constant.
Though the preferred embodiment is shown with lenses for electromagnetic waves, it should be kept in mind, that the invention is not limited to such lenses. By using a material with an appropriate refraction index even lenses, which are able to refract any other waves, e.g. sound waves, may be produced.
Fig. 1 shows a three-dimensional Luneburg lens 10, which works as radar reflector and as is state of the art. An incoming wave 11 is focussed by the lens 10 in such a way that the wave is focussed on a focus point 12. The wave is reflected by a reflector 13, whereby the reflected wave 14 is generated, which is led by the lens 10 in such a way, that it leaves the lens 10 in the same direction as the incoming wave 11 came from.
For leading the incoming wave 11 and the reflected wave 14 in the desired manner, it is necessary, that the relationship between the relative dielectric constant E(r) and the normalized radius r/a is given by E(r) = 2 - (r/a)2, (1) where r is the distance from the center point,
a is the radius of the lens 10, and
r/a = 1.0 at the outer surface of the lens.
Fig. 2 shows another application of the Luneburg lens 10. The difference between this embodiment and the embodiment of fig. 1 is, that here an incoming wave, such as 11a is led to a first focus point 12a and received by a first feeder horn 20a. In the same manner incoming waves 11b and 11c are led to focus points 12b, 12c and received by feeder horns 20 b, 20c respectively. The signals received by the feeder horns 20a, 20b, 20c are led to not shown receivers.
Of course the system according to fig. 2 can also work as transmitter antenna, if transmitters are connected to the feeder horns 20a, 20b, 20c.
According to the invention the three-dimensional lens 10 is produced by wrapping a dielectric material, preferably shaped as a thread. This is in principle shown in fig.3.
Starting at the center point of a lens 10' to be produced, a dielectric thread 21 is wrapped around the center point. Said thread has at least initially a relative dielectric constant E = 2.0. With an increasing distance from the center point the effective relative dielectric constant E(r) of the lens 10' to be produced decreases according to the formula (1).
The effective relative dielectric constant may be varied by a variation of the relative dielectric constant E of the thread. This could be achieved e.g. by a variation of the chemical composition or by a variation of the density of said thread with length. A variation of density with length could be achieved e.g. by a variation of pressure, proceeded by a press arranged before the lens 10' to be produced.
Another possibility of variation of the relative dielectric constant E may be achieved by a thread, created by several strands, whereby the number and/or the relative dielectric constant E of said strands may vary with length. It is still another possibility to vary the effective dielectric constant E by a variation of the amount of trapped air (E = 1).
This might be realized e.g. by a variation of the thickness of the thread, whereby the amount of trapped air is increased and thereby the effective relative dielectric constant is decreased.
It is another possibility to use a crimped thread, e.g. like it is shown in fig. 4a or 4b, which might be stretched by a variation of a stretching force used.
The dielectric constant of the thread may also be varied along the length with the aid of a metallic paint. In this case a low density dielectric thread of constant dielectric constant is used and as it is wrapped into the shape of the lens to be produced small areas of the thread are painted at a separation necessary to give the correct dielectric constant profile. That means for a desired value of the effective refraction index the thread used is painted with a paint, which may be metallic. Thickness, density or/a n d intensity of this paint may be varied. This is a simple method and will result in a relatively light lens.
It is to be said, that electromagnetic scattering by individual strands of the thread can be made negligible by keeping the radial dimensions of the thread 21 small.
Versions of the preferred embodiment may contain at least one of the following variations:
- instead of a thread, the material with the given refraction index may have any other appropriate shape, e.g. Like a strip, ribbon, or the Like
- by using an appropriate dielectric material, the lens to be produced may be able to refract other electromagnetic waves, such as visible or infrared light. - by an appropriate wrapping process, lenses with non- spherical shapes may be produced,
- the lens to be produced may have any desired relation
ship between the effective dielectric constant E(r) or the refraction index respectively and the normalized radius r/a, e.g. in that way, that the focus point 12 is inside or outside of the surface of the lens,
- the wrapping process may start at the surface of a core, which itself might have a variation of the refraction index and might be located around the center point,
- several threads may be used, one after the other and/or at the same time,
- by using a material with an appropriate refraction index even lenses, which are able to refract any other waves, e.g. acoustic waves, may be produced,
- a bonding agent may be used, which e.g. might be wrapped with the dielectric thread and when cured at an elevated temperature forms a more solid lens. of course, it might also be possible to dip the lens to be produced into an appropriate bonding agent during or/and after the wrapping process.
The invention presents a method for the fabrication or production of three-dimensional lenses with a variable effective refraction index by wrapping a material with a given refraction index, which may be constant or may vary with length. It is preferred, that said material has the shape of a thread, which might be cylindrical.
The preferred shapes of the lens to be produced are spherical or semi-spherical. The latter one can be achieved by an appropriate wrapping process or by cutting the spherical shape.
By the inventive method it is possible to produce the said lenses with a smooth varying of the refraction index.

Claims

C L A I M S
1. Method for the fabrication of three-dimensional lenses with a variable refraction index, characterized in that a material with a given refraction index is wrapped into the final shape of the lens to be produced.
2. Method according to claim 1, characterized in that the material with the given refraction index is shaped as a thread.
3. Method according to claim 1 or 2, characterized in that the final shape of the lens is spherical.
4. Method according to one of the claims 1 to 3, characterized in that the lens to be produced is a Luneburg-type or Eaton-Lippmann-type lens.
5. Method according to one of the claims 1 to 4, characterized in that the material with the given refraction index used has an actual change in the refraction index.
6. Method according to claim 5 characterized in that said thread itself is created by several strands and the actual change in the refraction index is achieved by a variation of the refraction index and/or the number of said strands.
7. Method according to one of the claims 2 to 6, characterized in that the thread used has a changing diameter with length.
8. Method according to one of the claims 1 to 7, characterized in that the material with the given refraction index is a dielectric material.
9. Method according to one of the claims 1 to 8, characterized in that the material to be wrapped is crimped.
10. Method according to claim 9, characterized in that a variation of the refraction index is achieved by stretching the crimped material with a given variable force.
11. Method according to one of the claims 1 to 10, characterized in that a bonding agent is used, which is wrapped with the material with a given refraction index.
12. Method according to one of the claims 1 to 11, characterized in that a bonding agent is used, in which the lens to be produced is dipped in during or/a n d after wrapping.
13. Method according to one of the claims 1 to 12, characterized in that small areas of the material to be wrapped are painted at a separation necessary to give the correct dielectric constant profile.
PCT/EP1991/001981 1990-10-29 1991-10-18 Method for the fabrication of lenses with a variable refraction index WO1992008254A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
JP3516866A JPH06502052A (en) 1990-10-29 1991-10-18 Manufacturing method of variable refractive index lens
DE69103764T DE69103764T2 (en) 1990-10-29 1991-10-18 METHOD FOR PRODUCING LENSES WITH VARIABLE BREAKING INDEX.
EP91918271A EP0555262B1 (en) 1990-10-29 1991-10-18 Method for the fabrication of lenses with a variable refraction index
US08/080,390 US5421848A (en) 1990-10-29 1991-10-18 Method for fabricating a lens having a variable refractive index
HK13797A HK13797A (en) 1990-10-29 1997-02-05 Method for the fabrication of lenses with a variable refraction index

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP90403051 1990-10-29
EP90403051.7 1990-10-29
AU87835/91A AU630329B3 (en) 1991-11-13 1991-11-13 Gas control valve

Publications (1)

Publication Number Publication Date
WO1992008254A1 true WO1992008254A1 (en) 1992-05-14

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PCT/EP1991/001981 WO1992008254A1 (en) 1990-10-29 1991-10-18 Method for the fabrication of lenses with a variable refraction index

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000076027A1 (en) * 1999-06-07 2000-12-14 Spike Broadband Systems, Inc. Axially symmetric gradient lenses and antenna systems employing same
EP1093201A1 (en) * 1999-10-13 2001-04-18 THOMSON multimedia Cable reel and electromagnetic wave communication device equipped with such a reel
ES2156756A1 (en) * 1999-09-30 2001-07-01 Arranz Gil Jose Luis Procedure for manually manufacturing spherical lenses

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3307196A (en) * 1962-12-28 1967-02-28 Armstrong Cork Co Luneberg type lens formed by spiral winding elongated strip of variable dielectric constant material
US4288337A (en) * 1977-05-02 1981-09-08 Tokyo Keiki Company Limited Lightweight materials having a high dielectric constant and their method of manufacture
US4482513A (en) * 1981-03-10 1984-11-13 General Dynamics, Pomona Division Method of molding foam/aluminum flake microwave lenses

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3307196A (en) * 1962-12-28 1967-02-28 Armstrong Cork Co Luneberg type lens formed by spiral winding elongated strip of variable dielectric constant material
US4288337A (en) * 1977-05-02 1981-09-08 Tokyo Keiki Company Limited Lightweight materials having a high dielectric constant and their method of manufacture
US4482513A (en) * 1981-03-10 1984-11-13 General Dynamics, Pomona Division Method of molding foam/aluminum flake microwave lenses

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000076027A1 (en) * 1999-06-07 2000-12-14 Spike Broadband Systems, Inc. Axially symmetric gradient lenses and antenna systems employing same
ES2156756A1 (en) * 1999-09-30 2001-07-01 Arranz Gil Jose Luis Procedure for manually manufacturing spherical lenses
EP1093201A1 (en) * 1999-10-13 2001-04-18 THOMSON multimedia Cable reel and electromagnetic wave communication device equipped with such a reel
US6595452B1 (en) 1999-10-13 2003-07-22 Thomson Licensing, S.A. Cable reel and electromagnetic wave communication device equipped with such a reel

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