WO2005040867A1 - Transformateur optique - Google Patents

Transformateur optique Download PDF

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Publication number
WO2005040867A1
WO2005040867A1 PCT/NO2004/000271 NO2004000271W WO2005040867A1 WO 2005040867 A1 WO2005040867 A1 WO 2005040867A1 NO 2004000271 W NO2004000271 W NO 2004000271W WO 2005040867 A1 WO2005040867 A1 WO 2005040867A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
optical
optical axis
axis
telescope
Prior art date
Application number
PCT/NO2004/000271
Other languages
English (en)
Inventor
Lars Oddvar Lierstuen
Original Assignee
Kongsberg Defence & Aerospace As
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
Priority claimed from NO20034063A external-priority patent/NO20034063D0/no
Application filed by Kongsberg Defence & Aerospace As filed Critical Kongsberg Defence & Aerospace As
Publication of WO2005040867A1 publication Critical patent/WO2005040867A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0938—Using specific optical elements
    • G02B27/095—Refractive optical elements
    • G02B27/0972—Prisms
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0911—Anamorphotic systems
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/04—Prisms

Definitions

  • the present invention relates to an optical unit, especially for increasing the efficiency of light coupling from a telescope into an optical waveguide or fiber, especially a single mode fiber which is the most demanding in such coupling.
  • Telescopes are used for collecting light propagating in free space. In some applications it is necessary to transfer light from the telescope to a single mode fiber. This is done in order to use optical components having this type of interface for treating the received light or to utilize the transmission capabilities of the fiber. Coupling of light into the fiber is performed by focusing the light from the telescope in to the fiber core with a lens. The F-number of the lens is essentially the only parameter one has to work on to optimize the coupling effect between the telescope and the fiber.
  • the field distribution has a shape of the Fourier transform of the light beam from the telescope.
  • the light beam has a circular cross section with a uniform intensity distribution.
  • the intensity distribution may be described by an Airy- function. This is a distribution that deviates from the approximate Gauss distribution of the fiber mode.
  • the coupling efficiency against a single mode fiber vil in such a case not be better than 81% (0.92dB coupling loss).
  • the opening diameter of the telescope is as large as possible, so that the ability to collect light is as good as possible.
  • Mirror optics is usually used in large telescopes.
  • Equation (1) give an approximate expression for the coupling loss between a telescope with a central obstruction and a single mode fiber, ref C.Ruilier, et.al., "A study of degraded light coupling into single-mode fibers ", In Astronomical Interferometry, SPIE vol.3350, pp. 319 - 329, 1998. It is here assumed that the fiber mode may be approximated with a Gaussian distribution..
  • D Diameter of the beam out from the telescope
  • ⁇ Relative obstruction diameter
  • f focal length of the lens
  • ⁇ 0 radius of the fiber mode
  • ⁇ Wvalength of the light
  • telescope designs which, based on mirror optics, does not have a secondary mirror positioned in the beam path.
  • the primary mirror is so-called "off-axis", i.e. that the focal point is outside the axis of the incoming light.
  • the secondary mirror then be positioned so as not to obstruct the incoming beam.
  • An object of the present invention is to increase the coupling efficiency between telescope and optical waveguide.
  • An optical unit for removing a shadow from a light beam in order to obtain a homogeneous light distribution in a light beam is described in JP 11176221. As will be discussed more in detail below with reference to the drawings this would increase the coupling efficiency to some degree. It is an object of this invention to provide means for improving the coupling efficiency further, also in cases without a shadow in the light beam.
  • an optical unit which comprises at least one rotation symmetric optical element positioned with the rotation axis in the optical axis and comprising two cone shaped surfaces, each with a constant angle relative to the optical axis.
  • the main principle according to the invention is turn a collimated beam inside out by moving the outer part of a collimated light beam with a homogeneous intensity profile, which then contains a relatively large fraction of the light, into the beam centre while moving the inner part of the beam out. This way the intensity profile is given a larger intensity in the beam centre. This is especially advantageous when the beam centre includes the shadow of a central obstruction in the beam, e.g.
  • the optical unit comprises two such optical elements, both having a collecting effect.
  • the optical elements are two refractive glass elements with a rotation symmetric, semi convex shape, both with conical surfaces having the same angles relative to the optical axis. Preferably the elements are identical.
  • Figure 3 illustrates the functional principle of a known optical unit.
  • Figure 4 illustrates an embodiment of the optical unit in figure 3 where a section of the two prisms is shown.
  • Figure 5 illustrates calculated coupling efficiency between telescope and fiber as a function of the obstruction radius with and without the optical unit according figure 3 and 4.
  • Figure 6 illustrates the light path in a mirror telescope with off axis mirrors, wherein the light comes in from the left and is here represented by beams i a plane through the optical axis.
  • Figure 7 illustrates the principle of the optical unit according to the invention.
  • Figure 8 illustrates a preferred embodiment of the invention wherein a section of the two prisms are shown based on the functionality illustrated in figure 7.
  • Figure 9 illustrates the invention being used on a light beam with a uniform cross section and on a light beams with a central obstruction.
  • Figure 10 illustrates the calculated coupling efficiency between a telescope and a single mode fiber with and without the optical unit according to the invention.
  • Figure 11 illustrates the invention realized using mirrors.
  • the secondary mirror creates a shadow in the light beam that reaches the primary mirror, making a discontinuity in the intensity distribution over the beam cross section.
  • the transmitted beam from the telescope is then focused toward the entrance of an optical waveguide (not shown) using a lens 3.
  • the coupling effect may be increased by providing an optical system that parallel displaces the beam radially according to the optical axis.
  • the invention consists of a cylindrical prism wherein the front is conical with an angle ⁇ relative to the optical axis.
  • the back surface is parallel to the front surface.
  • This element 4 is thus positioned in the light path between the secondary mirror 2 and the lens 3 in order to remove or reduce the shadow in the middle of the beams by shifting the light beams radially inward toward the optical axis while keeping the outgoing beams parallel to the optical axis.
  • Snell's law of refraction and geometrical considerations an expression may be evolved for the radial shift of the beam.
  • Figure 4 shows the principle for a design obtaining a shorter and lighter component by using to elements 4a,4b, wherein the first, 4a refracts the light inward toward the axis, and the second refracts it back toward a direction parallel with the optical axis. Still all the conical surfaces have the same angle against the optical axis and both elements have the same refractive index.
  • this design provides two surfaces refracting the light in toward the axis and two surfaces refracting the beam out from the optical axis.
  • the area where most of the shift happens is in air.
  • Figure 5 shows the coupling effect as a function of the relative obstruction radius. It is evident that a considerable improvement is obtained with the beam transformer.
  • the continuous line represents the coupling loss using the transformer, while the dotted line represents the coupling loss without this component. From a case where there is no obstruction in the telescope this version of the beams transformer has no function.
  • FIG. 7 A schematic illustration of the present invention is shown in figure 7.
  • the invention consists of a cylindrical prism where the front is conical with an angle ⁇ toward the optical axis.
  • the exit surface has the same shape as the entrance surface.
  • This element 5 is thus positioned in the beam path between the secondary mirror 2 and the lens 3 to change the intensity distribution in the beam by shifting the light beams 6 radially relative to the optical axis while keeping the exit beams parallel relative to the optical axis.
  • the lens 3 is adapted to the new beam diameter. Based on this solution an expression is found for the length of the prism.
  • Figure 8 shows the principle of a design where a shorter and lighter component is obtained by using two elements 5a,5b wherein the first 5a refracts the light in toward the optical axis and the second refracts the light back into a direction parallel to the optical axis. Still preferably all the cone surfaces have the same angle against the optical axis, and the elements have the same refractive index. Thus and advantage is obtained in that the elements are identical, which lowers the costs. In this design one gets four surfaces, all of them refracting the light in toward the axis. The area where most of the shift of the beam happens is in air. By varying the distance between the prisms the size of the remaining shadow is also varied.
  • Figure 9 illustrates the function of the invention and also how this embodiment will give a light beam without obstructions by adaptation to the outer diameter of the incoming beam.
  • the embodiment shown in figures 3 and 4 will, however, require adaptation to the obstruction diameter in the incoming beam. It is possible to evolve an expression for the intensity distribution I over the cross section on the exit of the beam transformer according to the invention:
  • Coupling efficiency is equal to the square of the overlap integral.
  • Figure 10 shows calculated coupling efficiency as a function of the relative obstruction ⁇ . For a beam without obstruction the coupling efficiency to a single mode fiber is -0.92 dB. Using the optical transformer the coupling efficiency to an optical fiber is calculated to be -0.35 dB. For a beam with a 40% obstruction the coupling efficiency is approximately -2.5 dB. Using the optical transformer the coupling efficiency is calculated to 0.43 dB. Thus a more than 2dB improvement.
  • the beams transformer may be used to shift the beams toward a common axis before focusing and coupling into a single mode fiber.
  • the optical unit may be combined with other elements for beam shaping and different numbers of prism elements and materials with different refractive indexes, so that it would be obvious for a person skilled in the art, based base on different applications of the invention. Even if single mode is mentioned as example here the person skilled in the art will realize that the invention may be used in other contexts with other wavelengths types as well.
  • the dimensions of the unit is preferably chosen so as to correspond to the width of the light beam, but, as is evident for a person skilled in the art, the parts extending outside the active part of the unit, or the width of the beam, is unimportant to the invention.
  • the rotation axis is defined relative to the active parts of the element. It should also be noted that although the unit preferably should be positioned in the optical axis it may also be usable in deviations from this position.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)
  • Glass Compositions (AREA)
  • Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
  • Communication Cables (AREA)

Abstract

L'invention concerne une unité optique destinée à la transformation de la lumière dans le but, par exemple, d'améliorer la connexion entre la lumière fournie par un télescope à miroir et un guide d'onde optique, le télescope étant conçu pour fournir un faisceau de sortie collimaté. L'unité optique comprend un élément symétrique rotatif de longueur donnée, disposé de façon que son axe de rotation soit dans l'axe optique et comprenant une première et une seconde surface conique présentant chacune un angle constant par rapport à l'axe optique. L'invention concerne également l'utilisation de l'unité optique dans des télescopes pour focaliser la lumière dans une fibre monomode, y compris des télescopes avec une obstruction centrale dans le faisceau de sortie, de type Cassegrain, par exemple.
PCT/NO2004/000271 2003-09-12 2004-09-10 Transformateur optique WO2005040867A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
NO20034063 2003-09-12
NO20034063A NO20034063D0 (no) 2003-09-12 2003-09-12 Optisk transformator
NO20035185 2003-11-21
NO20035185A NO320941B1 (no) 2003-09-12 2003-11-21 Optisk transformator

Publications (1)

Publication Number Publication Date
WO2005040867A1 true WO2005040867A1 (fr) 2005-05-06

Family

ID=30447743

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NO2004/000271 WO2005040867A1 (fr) 2003-09-12 2004-09-10 Transformateur optique

Country Status (2)

Country Link
NO (1) NO320941B1 (fr)
WO (1) WO2005040867A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006030421A1 (de) * 2006-06-29 2008-01-03 Carl Zeiss Optronics Gmbh Vorrichtung zur Übertragung optischer Signale
CN101320216B (zh) * 2008-06-18 2010-06-09 上海微电子装备有限公司 一种微光刻照明光瞳的整形结构
EP4092406A1 (fr) * 2021-05-19 2022-11-23 Hitachi High-Tech Analytical Science Finland Oy Ensemble optique pour spectroscopie d'émission optique

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4255021A (en) * 1979-04-20 1981-03-10 The United States Of America As Represented By The United States Department Of Energy Optical device with conical input and output prism faces
US4637691A (en) * 1983-02-07 1987-01-20 Nippon Kogaku K. K. Mirror converging-type illumination optical system
FR2661255A1 (fr) * 1990-04-24 1991-10-25 Azema Alain Systeme optique destine a transformer un faisceau de lumiere selon une repartition reglable et appareil de mise en óoeuvre.
US5382999A (en) * 1992-12-11 1995-01-17 Mitsubishi Denki Kabushiki Kaisha Optical pattern projecting apparatus
US5583342A (en) * 1993-06-03 1996-12-10 Hamamatsu Photonics K.K. Laser scanning optical system and laser scanning optical apparatus
JPH11176221A (ja) * 1997-12-12 1999-07-02 Moritex Corp 光源装置とこれに使用するアキシコンプリズム

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4255021A (en) * 1979-04-20 1981-03-10 The United States Of America As Represented By The United States Department Of Energy Optical device with conical input and output prism faces
US4637691A (en) * 1983-02-07 1987-01-20 Nippon Kogaku K. K. Mirror converging-type illumination optical system
FR2661255A1 (fr) * 1990-04-24 1991-10-25 Azema Alain Systeme optique destine a transformer un faisceau de lumiere selon une repartition reglable et appareil de mise en óoeuvre.
US5382999A (en) * 1992-12-11 1995-01-17 Mitsubishi Denki Kabushiki Kaisha Optical pattern projecting apparatus
US5583342A (en) * 1993-06-03 1996-12-10 Hamamatsu Photonics K.K. Laser scanning optical system and laser scanning optical apparatus
JPH11176221A (ja) * 1997-12-12 1999-07-02 Moritex Corp 光源装置とこれに使用するアキシコンプリズム

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 1999, no. 12 29 October 1999 (1999-10-29) *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006030421A1 (de) * 2006-06-29 2008-01-03 Carl Zeiss Optronics Gmbh Vorrichtung zur Übertragung optischer Signale
CN101320216B (zh) * 2008-06-18 2010-06-09 上海微电子装备有限公司 一种微光刻照明光瞳的整形结构
EP4092406A1 (fr) * 2021-05-19 2022-11-23 Hitachi High-Tech Analytical Science Finland Oy Ensemble optique pour spectroscopie d'émission optique

Also Published As

Publication number Publication date
NO20035185D0 (no) 2003-11-21
NO20035185L (no) 2005-03-14
NO320941B1 (no) 2006-02-13

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