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
  • G02B27/10—Beam splitting or combining systems
  • G02B27/14—Beam splitting or combining systems operating by reflection only
  • G02B27/145—Beam splitting or combining systems operating by reflection only having sequential partially reflecting surfaces
• • 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
  • G02B27/10—Beam splitting or combining systems
  • G02B27/108—Beam splitting or combining systems for sampling a portion of a beam or combining a small beam in a larger one, e.g. wherein the area ratio or power ratio of the divided beams significantly differs from unity, without spectral selectivity
• • 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
  • G02B27/10—Beam splitting or combining systems
  • G02B27/14—Beam splitting or combining systems operating by reflection only
  • G02B27/144—Beam splitting or combining systems operating by reflection only using partially transparent surfaces without spectral selectivity
• • 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 a device for sampling a plurality of parts of a light beam, in particular a laser beam.
• This device comprises at least one optical component which is designed to generate two optical samples of a parallel ray light beam, without any parasitic image.
• the invention is particularly applicable to the diagnosis of laser beams.
• the above-mentioned component makes it possible to generate three diagnostic channels that are distinct, completely decoupled and without parasitic image.
• the photometry of the channels can be managed in a conventional manner, by the type of semi-reflective treatment that is deposited on each side of the component.
• a blade in English, flat 2 (FIG. 1) having two plane and parallel faces, or a prismatic plate 4 (FIG. 2), or a beam splitter cube (in English, beamsplitter cube) 6 (FIG. 3), or a diffractive component 8 (FIG. 4).
• FIGS. 1 to 3 generate only one sampling channel 10 from an incident light beam 12, and the diffractive component 8 generates as many samples 14 as there are diffraction orders.
• the blade with flat and parallel faces 2 generally generates several parasitic beams.
• Figure 1 we see one of these, which is parallel to the beam 16 transmitted by the cube 2, and two other parasitic beams 18 which are parallel to the beam 10 reflected by this cube.
• FIG. 2 shows that the parasitic beams 20 and 22 have directions which are respectively separated from that of the reflected beam 10 and that of the transmitted beam 24, but the separation is weak and the transmitted beam 24 is deflected, which complicates the mechanical integration of the analysis system (not shown) using the prismatic plate.
• the beam splitter cube 6 solves the problem of parasitic imaging quite well. Indeed, we see in Figure 3 two parasitic beams 26 and 28 which are respectively parallel to the reflected beam 10 and the transmitted beam 30, and the maximum parasitic amplitude is typically one hundred times lower than that of the incident beam 12. But the cube 6 generates only a sample.
• the diffractive component 8 generates, for its part, several samples 14 and perfectly solves the problem of parasitic imaging. However, it temporally alters a pulsed light beam and scatters a beam that is not perfectly monomode. It is then necessary to use two diffractive components to partially solve these problems of alteration and dispersion.
• the object of the present invention is to overcome the above disadvantages by proposing a device which is capable of providing at least two samples devoid of parasitic images, from an incident light beam, and which allows the easy integration of a system. beam diagnostics using this device.
• the present invention relates to a device for sampling a plurality of parts of a light beam, this device being characterized in that it comprises at least one optical component comprising a blade of material transparent to the light beam , this blade having first and second faces which are plane and parallel, and a third face which is flat and forms a dihedron with the first face, the angle of this dihedral being equal to ⁇ - ⁇ , with
• n the refractive index of the material, so that by sending the light beam on the first face, at an angle of incidence equal to Arcsin (n.sin ( ⁇ )), recovering a first part taken and a second part removed and most of the light beam.
• the third face is made reflective vis-à-vis the light beam.
• the first and second faces can be processed so as to have reflection coefficients determined vis-à-vis the light beam.
• the angle ⁇ may be equal to Arcsin (V2 / (2n)).
• the device according to the invention may comprise at least two copies of said component, placed one after the other, so as to increase the number of parts removed.
• the present invention also relates to a method of sampling a plurality of parts of a light beam, this method using the device object of the invention.
• FIGS. 1 to 4 are schematic views of known beam picking devices and have already been described
• FIG. 5 is a schematic top view of a particular embodiment; of the device which is the subject of the invention.
• FIG. 6 is a schematic view of another device according to the invention.
• the device according to the invention which is schematically represented in FIG. 5, comprises a single optical component 32.
• This component is capable of producing two samples devoid of a parasitic image from an incident light beam 34 which is monochromatic and parallel, that is to say whose rays are parallel, such as for example a laser beam.
• the component allows the easy integration of a diagnostic device comprising this component.
• the component 32 is a prism that results from a flat-faced and parallel plate which has been truncated.
• the prism 32 is made of a material that is transparent to the incident beam 34; and it has a first face 36 and a second face 38 which are flat and parallel to each other.
• the prism has a third face 40 which forms a dihedron with the first face 34.
• the faces 36, 38 and 40 are thus perpendicular to the plane of this figure 5.
• the angle A of the dihedral is equal to ⁇ - ⁇ where ⁇ is the truncation angle of the blade, the truncated portion being delimited by dotted lines on FIG. 5. This angle ⁇ is such that:
• n the refractive index of the material, at the wavelength of the beam 34.
• a first portion 44 of the beam 34 is picked up by reflection on the face 36 but the bulk of the beam 34 leads to the refracted beam 46.
• the latter emerges from the face 38 along a beam 48 which is parallel to the beam 34.
• the latter is propagated towards the face 40 in a straight line which is perpendicular to this face 40, and is therefore reflected in part on it, following the same line, then emerges from the face 38 along a beam 52 which constitutes a second portion taken from the incident beam 34.
• Each of the beams 48 and 52 forms an angle i. with a normal 54 to the face 38.
• the major part 56 of the beam 50 emerges from the face 40, perpendicular to the latter, and can thus constitute a third sampling path. However, the existence of this part 56 would lead to a low intensity for the second part taken, constituted by the beam 52.
• the face 40 is made reflective, for example by forming a metal layer 58 on this face, so as not to lose a signal on the sampling path 52.
• the two samples formed by the beams 44 and 52 each carry between 2% and 8% of the incident energy, according to the polarization of the beam 34.
• this incident beam 34 can perform a treatment of the faces 36 and 38 to adjust the value of the reflection coefficient of these faces, if necessary.
• the two sampling channels 44 and 52 are perpendicular to the incident beam 34, which facilitates the mechanical integration of the other components (not shown) of the beam diagnostic system.
• the angle ⁇ is equal to Arcsin (1 / (n S)).
• the compact component 32 generates two samples 44 and 52 from the beam 34, without any parasitic image for the analysis system, which is very interesting for analyzing the beam 34. Moreover, this component is monobloc and very simple to manufacture. , and it can be serialized to multiply the number of channels.
• Figure 6 shows two components 70 and 72 which are placed one after the other. These components are of the type of the component 32.
• This beam 80 reaches the component 72 whose first face is facing the second face of the component 70 and parallel thereto.
• the component 72 provides two samples 82 and 84.
• the beam transmitted by the component 72 has the reference 85.
• parasitic light beams 86, 88 and 90 which result from reflections of the light in the prism 32.
• the beam 88 is directed towards the face 92 of the prism, face which connects the faces 36 and 38 as seen. This face 92 is unpolished to prevent specular reflection of the beam 88.
• the single parasite return (beam 90) undergoes two reflections, and is therefore very weak; in addition, it returns to the source (not shown) of the beam 34, which does not disturb the measurement. If necessary, a slight modification of one of the angles i or ⁇ makes it possible to modify the direction of this parasitic return.
• the component 32 laterally shifts the main beam: the beam 48 is shifted relative to the beam 34. But this can be corrected by a second component identical to the component 32 and mounted symmetrically. In this case, and repeating the notations of FIG. 6, the beam 85 emerges in the extension of the beams 74. It should also be noted that, like all the reflection sampling diagnostics, the component 34 can modify the state of polarization of a beam if the incident electromagnetic field is not TE or TM.
• the device according to the invention can be used with any laser beam on which it is desired to make several samples.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)

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• 2006
  • 2006-12-28 FR FR0656021A patent/FR2910979B1/fr not_active Expired - Fee Related
• 2007
  • 2007-12-24 EP EP07858133A patent/EP2104871A1/de not_active Ceased
  • 2007-12-24 WO PCT/EP2007/064535 patent/WO2008080915A1/fr not_active Ceased
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