WO2005040740A1 - Spectrometre a resolution elevee - Google Patents

Spectrometre a resolution elevee Download PDF

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Publication number
WO2005040740A1
WO2005040740A1 PCT/EP2004/009914 EP2004009914W WO2005040740A1 WO 2005040740 A1 WO2005040740 A1 WO 2005040740A1 EP 2004009914 W EP2004009914 W EP 2004009914W WO 2005040740 A1 WO2005040740 A1 WO 2005040740A1
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WO
WIPO (PCT)
Prior art keywords
dispersing element
spectrometer according
spectrometer
detector
grating
Prior art date
Application number
PCT/EP2004/009914
Other languages
German (de)
English (en)
Inventor
Ross Helmut Becker
Stefan Florek
Günter WESEMANN
Original Assignee
Gesellschaft zur Förderung angewandter Optik, Optoelektronik, Quantenelektronik und Spektroskopie e.V.
Gesellschaft zur Förderung der Spektrochemie und angewandten Spektroskopie e.V.
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 Gesellschaft zur Förderung angewandter Optik, Optoelektronik, Quantenelektronik und Spektroskopie e.V., Gesellschaft zur Förderung der Spektrochemie und angewandten Spektroskopie e.V. filed Critical Gesellschaft zur Förderung angewandter Optik, Optoelektronik, Quantenelektronik und Spektroskopie e.V.
Publication of WO2005040740A1 publication Critical patent/WO2005040740A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/12—Generating the spectrum; Monochromators
    • G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
    • G01J3/1809—Echelle gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/12—Generating the spectrum; Monochromators
    • G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
    • G01J3/22—Littrow mirror spectrometers

Definitions

  • the invention relates to a high-resolution spectrometer with an entrance slit, a dispersing element, camera optics, and a detector arrangement with a
  • Detector which are arranged similar to one another in a manner similar to a Littrow arrangement so that radiation which enters the spectrometer through the entrance slit can be conducted onto the dispersing element by means of the camera optics, and then can be conducted back up to a small angle via the same camera optics and can be focused on the detector, means being provided for producing a multiple dispersion by the dispersing element.
  • a high-resolution spectrometer is known from DE 199 61 908 C2, in which
  • Radiation from an entrance slit is directed onto an Echelle grating by means of camera optics.
  • the Echelle grating is positioned so that the single dispersed beam from the Echelle grating first to one to create a double grating pass Plane mirror is bent. The radiation is reflected back at the plane mirror. The beam then runs again over the grating and back over the camera optics towards a detector. By slightly tilting the plane mirror, the radiation is directed out of the main plane of the beam path.
  • the location of the spectrum which is formed from the monochromatic images of the entrance slit, lies above or below the entrance slit. There the spectrum is registered by means of a detector.
  • the beam path can be changed by a suitable grating rotation so that the beam runs back directly from the grating. Then a simple dispersion is realized.
  • the theoretical resolution R in a grating spectrometer is determined by the total number of grating grooves N and the diffraction order m. With double passage over the grating, an increased spectral resolution can be achieved compared to the single passage.
  • the object of the invention is a high-resolution spectrometer of the type mentioned
  • the object is achieved in that the means for producing the multiple dispersion comprise at least two reflective, flat surfaces which form a right angle with one another and which the dispersed and focused radiation first in the direction of one of the other reflecting surfaces and then in the direction of reflect the dispersing element back, and which are arranged relative to the entry slit in such a way that the entry slit is in the intersection of the planes defined by the reflecting surfaces.
  • the incoming beam runs from the entrance slit onto camera optics.
  • the camera optics generate a parallel beam.
  • the beam passes over the dispersing element and is dispersed there for the first time.
  • the dispersed radiation runs from the dispersing element back to the camera optics, which focuses the radiation in the plane of the entrance slit.
  • the returning jet does not run back exactly from itself from the dispersing element, but forms a small angle with the incoming jet within the dispersion plane.
  • the dispersion level is defined by the incoming and the deflected beam at the dispersing element. The angle is so small that the aberrations remain small.
  • Within the dispersion plane there is a reflecting surface on both sides of the entrance slit, for example two small plane mirrors.
  • the returning beam does not run back to the entrance slit, but hits one of the reflecting surfaces.
  • the reflective surfaces form a right angle with each other.
  • the returning beam is therefore deflected by the first reflecting surface before the focus and strikes the second reflecting surface. There the beam is redirected again. The image is reversed. After the twofold deflection, the beam runs back into itself a small distance offset from one another.
  • the parallel incoming jet hits the dispersing element for a second time, where it is redispersed.
  • the beam that returns again is then directed past the edge of the reflecting surface next to the entrance slit onto a detector which is located directly next to the reflecting surface in the plane of the entrance slit.
  • the angle of deflection at the dispersing element is reduced so that the first returning beam strikes the reflecting surface closer to the entrance slit.
  • the second and each further returning beam strikes the reflecting surface somewhat offset further away until the last returning beam falls past the reflecting surface onto the detector as described above.
  • the resolution can therefore be increased significantly.
  • the size of the components does not change.
  • the optical beam path for all passes between the
  • the dispersing element can be formed by a diffraction grating, in particular an Echeller grating.
  • a prism can be used.
  • the reflecting surfaces can be formed by mirrors. Instead of two mirrors arranged at right angles to each other, the reflecting surfaces of a prism can also be used, which form a right angle.
  • the edge on which the right angle is formed the light can enter the spectrometer through the prism. This flattening then takes up the entry gap or it is formed directly by it.
  • a further reflecting surface is provided, and the dispersing element is arranged between the camera optics and this further reflecting surface in such a way that the dispersed light from the dispersing
  • Element is first directed directly onto the reflective surface, then back onto the dispersing element and only then back onto the camera optics. Then a double pass on the dispersing element is realized in one cycle.
  • the camera optics is preferably formed by a parabolic mirror. This results in a compact arrangement of high image quality without chromatic errors and with low loss n.
  • the detector arrangement comprises an optical system for enlarged imaging of the spectrum on the picture elements of the detector.
  • This optic can be formed by two cylindrical lenses or mirrors. With such an optical system, the high-resolution spectrum is enlarged, that is, in particular with the height remaining the same, "pulled apart" in width. Then the spectrum can be used larger detector elements are recorded without the resolution deteriorating.
  • the dispersing element is preferably rotatable about an axis perpendicular to the dispersion plane.
  • the rotation can be carried out using suitable means, for example a
  • Stepper motor and a computer can be automated. Then the change of the inspection area, i.e. of the spectral range under consideration can be carried out in a particularly simple manner. For example, if the spectral environment of a line is to be examined, the inspection area can be enlarged by placing the grating or prism on a single pass. The returning beam runs from
  • the reflecting surfaces each have an angle of 45 degrees to the optical axis of the light beam entering through the entrance slit. Then the arrangement is arranged symmetrically about the optical axis and the imaging errors are small. A slight deviation due to misalignment
  • Rotation around an axis that is perpendicular to the dispersion plane does not lead to a disturbing change in the beam paths.
  • the spectrometer is particularly well suited for use in determining spectral profiles of laser radiation.
  • Laser radiation is generally narrow-band and therefore requires particularly high-resolution spectrometers for profile measurement.
  • the spectral profile can also be monitored and stabilized by means of such a spectrometer by adapting the operating parameters of the laser.
  • Embodiments of the invention are the subject of the dependent claims.
  • Fig.l is a schematic representation of a high-resolution grating spectrometer with retroreflectors, in which the course of the center beam is drawn for a double grating pass.
  • FIG. 2 is a schematic illustration of the spectrometer from FIG. 1, in which the course of the marginal rays is drawn for a simple grating passage.
  • FIG. 3 is a schematic illustration of the spectrometer from FIGS. 1 and 2, in which the course of the center beam for a simple grating passage is shown.
  • FIG. 5 shows the spectral line from FIG. 4 with a double lattice passage
  • Fig. 6 shows the beam path in the area of the rescue reflectors with five times the grating
  • FIG. 7 is a schematic representation of an alternative high-resolution grating spectrometer, in which the beam is first dispersed on a plane mirror and then passes over the grating again.
  • FIGS. 1 to 3 are schematic illustrations of the spectrometer from FIGS. 1 to 3, in which the course of the center beam for a triple lattice passage is drawn
  • a high-resolution spectrometer 10 is shown schematically in FIG.
  • the spectrometer 10 comprises an entrance slit 12, a camera mirror 14, an echelle Grating 16, two plane mirrors 18 and 20, and a detector 22.
  • the center j beam 24 of the radiation entering through the entrance slit 12 is shown.
  • Arrows 1-8 indicate the direction of travel of the center beam, the sequence of the beam path corresponding to the numbering 1-8.
  • the camera mirror 14 is designed as an off-axis parabolic mirror. Due to the parabolically shaped reflecting surface 26, the divergent radiation is parallelized and deflected in the direction of the Echelle grating 16. This is shown by an arrow 2.
  • the surface 26 is provided with a mirror coating, which also has a high reflectivity even in the UV range below 200 nm.
  • Parabolic mirror 14 on the beam The incoming, parallel beam hits the grating 16 and is dispersed there.
  • the grid 16 is rotatably supported about an axis 28.
  • the grating 16 is designed as an Echelle grating. A large blaze angle at the Echelle grating 16 produces a large path difference 38 between the marginal rays 2 'and 2 ". This causes the radiation to be highly dispersed in a high diffraction order. In this way, a high resolution is achieved in one pass.
  • the grating 16 is positioned analogously to a Littrow arrangement in such a way that the center beam, designated 3 in FIG. 1, has a wavelength down to a small angle ⁇ . In practice, the angle ⁇ is much smaller than shown here.
  • Entry slit 12 arranged in the beam path a first plane mirror 18.
  • the plane mirror 18 is arranged at an angle of + 45 ° (clockwise) to the optical axis corresponding to the center beam 14.
  • the returning beam is therefore deflected at right angles upwards in FIG. 1.
  • the focus is then on the optical axis of the input beam (arrow 1).
  • a further plane mirror 20 is arranged on the other side of the entry gap 12. This plane mirror is arranged at an angle of -45 ° (clockwise) to the optical axis.
  • the mirror planes of the mirrors 18 and 20 form a right angle and intersect along an intersection line that coincides with the center line of the entry slit 12.
  • the beam is deflected at a right angle again at this mirror 20.
  • the beam travels back by a distance 32 in the direction of the camera mirror 14. This is shown by an arrow 5.
  • the image is reversed during the double reflection at the plane mirrors 18 and 20. This means that the path difference 38 of the marginal rays on the grid is added. As a result, the resolution is maximally increased by the second grating passage that now follows.
  • the incoming beam 5 is again parallelized by the camera mirror 14 (FIG. 2) and reflected as a parallel beam 6 in the direction of the grating 16.
  • the twice-dispersed beam 7 runs back to the camera mirror 14.
  • the detector arrangement 22 can consist of a simple line or area detector. Any common detector such as a photodiode array, a CCD or a CID detector is suitable here. However, light guides can also be arranged there, or a magnifying optic consisting of two cylindrical lenses or mirrors with which the image of the entrance slit is enlarged. The enlarged image is then recorded using one of the detectors listed above. This has the advantage that commercially available detectors with larger detector elements can be used without losing their resolution.
  • the grid 16 is arranged rotatable about an axis 28. By rotating it into a suitable position, the beam can be aligned so that the angle ⁇ between the incoming and outgoing beam becomes somewhat larger. Then the returning beam is no longer incident on the mirror 18, but directly on the detector 22. This case is shown in FIG.
  • FIGS. 4 and 5 The effect on the resolution is shown in FIGS. 4 and 5.
  • a laser line 40 consisting of two peaks is not resolved in FIG. 4.
  • a larger area is recorded, in which another line 42 lies.
  • Such a 'spectrum is obtained when the grating is shown in FIG. 3
  • Position. 5 shows a spectrum for the same laser line with higher resolution.
  • Line 42 from FIG. 4 cannot be detected because the inspection area has shrunk.
  • the line components 44 and 46 of line 40 are now completely separated.
  • the profile can be determined with sufficient accuracy.
  • the higher resolution is achieved by the grid 16 in a
  • the grating 16 is rotated into a position in which the angle ⁇ is even smaller.
  • the beam then travels back and forth between the mirrors 18, 20 and the grating until it passes the mirror 18 and hits the detector 22. 6 shows a situation for a 5-fold lattice passage.
  • the beam 50 runs from the entrance slit 12 to the grating 16, is dispersed there and runs back offset by a small angle.
  • the simply dispersed, returning beam 52 is focused by the camera mirror 14 and on
  • the focus 53 lies on the optical axis of the beam 50 halfway between the mirrors 18 and 20.
  • the beam is reflected again at the mirror 18 and runs back to the grating.
  • the returning beam is labeled 54.
  • the beam is redispersed on the grating.
  • the returning beam 56 forms an even larger angle than the beam 50, so that it strikes the mirror 20 further out. There are just enough revolutions until the beam hits the edge 58 of the mirror 20 runs past on the detector. In the example of Fig. 6, 5 grid passes are realized.
  • the number of grid passes can therefore be set by rotating the grid.
  • the aberration caused by the wobble ⁇ is small, since the detector is arranged directly next to the entrance slit and the mirrors.
  • the reflection losses can be kept low.
  • the parabolic mirror is rotated about an axis perpendicular to the dispersion plane. However, this is generally not necessary.
  • FIG. 7 shows an embodiment of the above exemplary embodiment.
  • a plane mirror 62 is arranged behind the grating.
  • the beam first runs from the grating 16 to the plane mirror 62 and from there back to the grating 16. There the radiation is diffracted again. There is therefore a double pass at the grating each time before the beam runs back in the direction of the mirrors 18, 20 or the detector 22.
  • the advantage of this arrangement is that with only one additional, comparatively inexpensive, optical component, the total number of reflections can be reduced with the same number of grating passes. Dust or scratches on the mirrors then cause less stray light.
  • the resolution can be set by rotating the grating.
  • the grating can be brought into the position in which there is no passage through the mirror 62.
  • the number of passes can be adjusted via the number of reflections on the mirrors 18 and 20.
  • 8 shows the case in which a triple lattice passage is realized.
  • the beam runs according to the numbers 1-12 to the grating and back to the spatulas 18 and 20. It can be seen in comparison to the arrangement in Fig.l that only the grating position of the grating 16 has changed in the arrangement. All other optical components remain the same.
  • the grid 16 was rotated about the axis 28 by a small angle. This rotation can be done manually or computer controlled with a stepper motor.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Spectrometry And Color Measurement (AREA)

Abstract

L'invention concerne un spectromètre à résolution élevée (10) pourvu d'une fente d'entrée (12), d'un élément de dispersion (16), d'une optique de caméra (14) et d'un système de détecteur comportant un détecteur (22). Les composants optiques sont disposés à la manière d'un dispositif de Littrow les uns par rapport aux autres de telle manière qu'un rayonnement pénétrant dans le spectromètre (10) au travers de la fente d'entrée (12) peut être guidé par l'intermédiaire de l'optique de caméra (14) sur l'élément de dispersion (16) et réfléchi à un angle faible (y), puis focalisé sur le détecteur (22). Le spectromètre selon l'invention comporte par ailleurs des éléments (18, 20) destinés à produire une dispersion multiple par l'intermédiaire de l'élément de dispersion (16). Ledit spectromètre est caractérisé en ce que lesdits éléments comportent au moins deux surfaces réflectrices plates (18, 20) formant un angle droit, réfléchissant le rayonnement dispersé et focalisé (3) d'abord en direction de l'autre surface réflectrice, puis en direction de l'élément de dispersion (16). Lesdites surfaces réflectrices sont disposées de telle manière que la fente d'entrée (12) se trouve à l'intersection des plans définis par les surfaces réflectrices (18, 20).
PCT/EP2004/009914 2003-10-10 2004-09-06 Spectrometre a resolution elevee WO2005040740A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10347862A DE10347862B4 (de) 2003-10-10 2003-10-10 Hochauflösendes Spektrometer
DE10347862.0 2003-10-10

Publications (1)

Publication Number Publication Date
WO2005040740A1 true WO2005040740A1 (fr) 2005-05-06

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WO (1) WO2005040740A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117647311A (zh) * 2024-01-30 2024-03-05 中国海洋大学 一种飞米级超高光谱分辨率光谱仪光学***及其应用

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009059280A1 (de) 2009-12-22 2011-06-30 Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., 44139 Spektrometeranordnung
DE102011082469B4 (de) * 2011-09-09 2015-02-26 Oxford Instruments Analytical GmbH Spektrometer mit wenigstens einem Zerstreuungselement
DE102012101019B4 (de) 2012-02-08 2015-03-12 Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V. Spektrometer-Anordnung für UV-VIS

Citations (2)

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Publication number Priority date Publication date Assignee Title
US2652742A (en) * 1950-11-09 1953-09-22 Commw Scient Ind Res Org Monochromator
DE19961908A1 (de) * 1999-12-20 2001-08-16 Ges Zur Foerderung Angewandter Optik Optoelektronik Quantenelektronik & Spektroskopie Ev Hochauflösendes Littrow-Spektrometer und Verfahren zur quasi-simultanen Bestimmung einer Wellenlänge und eines Linienprofils

Family Cites Families (3)

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Publication number Priority date Publication date Assignee Title
US2868063A (en) * 1957-05-16 1959-01-13 Leeds & Northrup Co Adjustable mirror support in successive dispersion monochromator
DE4118760A1 (de) * 1991-06-06 1992-12-10 Zentralinstitut Fuer Optik Und Echelle-doppelmonochromator
JP2001304963A (ja) * 2000-04-21 2001-10-31 Ando Electric Co Ltd ４段式分光器

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2652742A (en) * 1950-11-09 1953-09-22 Commw Scient Ind Res Org Monochromator
DE19961908A1 (de) * 1999-12-20 2001-08-16 Ges Zur Foerderung Angewandter Optik Optoelektronik Quantenelektronik & Spektroskopie Ev Hochauflösendes Littrow-Spektrometer und Verfahren zur quasi-simultanen Bestimmung einer Wellenlänge und eines Linienprofils

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117647311A (zh) * 2024-01-30 2024-03-05 中国海洋大学 一种飞米级超高光谱分辨率光谱仪光学***及其应用
CN117647311B (zh) * 2024-01-30 2024-04-19 中国海洋大学 一种飞米级超高光谱分辨率光谱仪光学***及其应用

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DE10347862A1 (de) 2005-05-19
DE10347862B4 (de) 2006-07-13

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