DE102007011324A1 - Spectrometer i.e. oscillating mirror spectrometer, for e.g. optical spectrometry, has oscillating mirror provided downstream of optical path for imaging spectrum of radiation, where mirror is provided in area of optical path - Google Patents

Abstract

The spectrometer has a radiation source, an entrance slit (1) and an imaging diffraction grating (2) that are provided in a path of rays. An optical field lens (3), an imaging lens (4), an oscillating mirror (5) and a detector lens (6) e.g. convex lens, are provided downstream of an optical path for imaging a spectrum of radiation passing via the entrance slit to a detector (7) e.g. line detector. The mirror is provided in an area of the optical path. The grating is designed as a hybrid-optical element having a nano-structured aspherical or free forming surface.

Description

The The invention relates to a spectrometer for optical Spectrometry, in particular a vibrating mirror spectrometer for detection biological and chemical agents. This spectrometer is based on the use of micro-electro-mechanical systems (MEMS).

In known classical spectrometers incident through a Eintrittsapertur (entrance slit) in the spectrometer light hits a diffraction grating, which is advantageously designed as an imaging reflection grating. However, it is also possible to use reflective planters or transmission gratings. According to the known lattice equation, the spectral components of the irradiated light influenced by the sample are deflected into different spatial directions by these lattices, thus resulting in a spectrum which is imaged on a detector, as is known, for example, from US Pat EP 0 167 750 can be seen. The resulting detector signals are then processed and analyzed accordingly for analysis purposes.

In the article of F. Zimmer, H. Grueger, A. Heberer, H. Schenk, H. Lakner, A. Kenda, W. Scherf: "Development of high-efficient NIR scanning gratings for spectroscopic applications", Proceedings of SPIE, Vol. 6114 , 611407 (2006), 1-4 , a spectrometer for the near infrared range of 900 to 2500 nm is described and shown schematically, which comprises two imaging concave mirrors and a scanning diffraction grating. This diffraction grating is moved by a pulsed voltage and has a lattice structure of modified micromirrors. In this case, the light irradiated through a gap is directed by the one concave mirror onto the diffraction grating. The spectrally diffracted light diffracted by the grating is directed by the second concave mirror through an aperture onto a photodiode or onto a detector. Through the moving grid, the spectral components of the light are imaged in succession on the photodiode. The signals generated by the photodiode are supplied in corresponding devices of an evaluation.

at This arrangement is the relatively small area of the grid a major disadvantage for the performance of the spectrometer, because the spectral resolution of both the lattice constant depends also on the number of interfering partial beams, which largely determined by the grid size becomes. Furthermore, it is disadvantageous that the diffraction structure during the manufacturing process are applied to the micromirror must, which limits design freedoms of this grid become. Thus, specially adapted grid profile shapes (eg. Blazes) and the diffraction efficiencies are not sufficiently large for all application requirements.

In the DE 10 2004 046 983 A1 describe an apparatus and a method for the spectroscopic detection and determination of biological and chemical objects and samples by means of radiation in the near and middle infrared range. The device comprises a radiation source, a substantially parabolic reflector, a micromirror formed as a vibrating mirror, a diffraction grating, a detector and a control device.

Reflector, Micromirror and the diffraction grating are arranged so that by the radiation emitted by the radiation source passes through a sample or so reflected by the sample is that the radiation from the reflector is directed by reflection on the micromirror on the diffraction grating and that the diffracted radiation is due to reflection at the micromirror and is directed at the reflector on the detector. In this device the oscillating mirror is so arranged in the beam path that a parallel beam is deflected or scanned. To a larger one Aperture of the spectrometer must realize the dimensions be designed to be large, which is disadvantageous is.

Of the The invention is therefore based on the object, a vibrating mirror spectrometer to create, which has a simple and space-saving design and the use specifically for different uses adapted grating profile shapes of the diffraction grating and sufficiently large Diffraction efficiencies for a wide variety of application requirements allows.

According to the invention this task with a equipped with the features of the main claim Oscillation mirror spectrometer solved. In the dependent claims are further embodiments and details of the invention Spectrometer disclosed.

So it is advantageous that at least one of the arranged in the spectrometer Lens is an aspherical or free-form lens.

Especially It is advantageous that the detector element as a point detector or is designed as a linear detector. So that can the spectrometer is equipped with a simply constructed detector element become.

Advantageous is also that for the precise focusing of the beam path on the detector element the oscillating mirror a convex lens, in particular a plano-convex lens, is arranged downstream.

It is also advantageous if one with the point detector and the Oscillation mirror connected control device is provided for detecting the Position of the oscillating mirror and to ensure a synchronous detection of the occurring light intensities the radiation to be evaluated.

to Simplification and miniaturization of the spectrometer is advantageous that the imaging grating is formed as a hybrid optical element which is a nanostructured aspheric or freeform surface has.

Advantageous is still, if more imaging mirror surfaces for Avoidance of interface reflections, stray light and / or chromatic aberrations in the optical path of the spectrometer are provided.

Advantageous The grid can also be designed as a plan or hollow grid.

A advantageous embodiment of the invention results, if, in addition to the diffraction grating, a dispersion prism is arranged in the beam path whose dispersion direction is orthogonal to the dispersion direction of the diffraction grating, and if a line-shaped detector for the detection of the spectral Shares of light or radiation is provided.

Advantageous it may also be, if the entrance slit point or linear is trained.

at This oscillating mirror spectrometer forms a so-called relay optics different spectral components of the incident light on one, in one dimension about an axis perpendicular to the light incidence plane movable oscillating mirror, according to the law of reflection this spectrum is passed over a detector. Through the detector the intensity of the per unit time determined by incident light, and by a designated electronic Control will get this obtained intensity information implemented and further processed. The angular position of the oscillating mirror is monitored synchronously and included in the evaluation.

The Invention will hereinafter be an embodiment be explained in more detail. In the drawing is the illustrated basic structure of a vibrating mirror spectrometer.

This in 1 In principle, the spectrometer comprises an entrance slit 1 by which the radiation influenced by an object to be examined and irradiated by a radiation source (not shown) is introduced into the spectrometer.

The entrance slit 1 and a downstream of the beam path, imaging diffraction grating 2 form, as already known from the prior art, a polychromator. This polychromator could in principle also be replaced by other known polychromator arrangements. At the optical output of this polychromator arises in a grid aperture plane 9 a spectrum, which in the figure by three pixels 9a ; 9b and 9c are illustrated. A downstream field lens 3 , which are near the grid aperture plane 9 is arranged, this level forms on a vibrating mirror 5 from. An arranged in the beam path collimator lens 4 , which is advantageously designed as an aspherical lens, shapes the radiation of each individual wavelength into a nearly parallel beam. The beams of all wavelengths are at the location of a downstream oscillating mirror 5 united. These meet at different angles on the vibrating mirror 5 on and are reflected by this. A downstream detector lens 6 , which is represented in the figure as a plano-convex lens, selects the rays which come almost from one direction and focuses them on a detector 7 , Depending on the angular position of the oscillating mirror 5 , whose angular position moves by ± 10 ° about a central position, thus becomes an incident beam to the detector 7 which is a point or line detector, with which the beams of the individual wavelengths are selected. It is also a control unit 8th provided, which with the detector 7 connected is. This control unit 8th controls the movement of the oscillating mirror 5 and measures the mirror position. They link the measured detector signals with the mirror position or with the associated wavelength. The control unit 8th Periodically, the signal values or average values of several periods belonging to each mirror position or wavelength are forwarded to an evaluation unit, not shown in the figure, with which the control unit 8th connected is.

In place of the oscillating mirror 8th It is also possible to provide a mirror which can be rotated about an axis. Similarly, the field lens 3 , the collimator lens 4 and the detector lens 6 or at least one of these lenses are replaced by concave mirrors.

In a modification of this illustrated principle, however, it is also possible to integrate many of the optical effects of the optical components used as hybid-optical element in the diffraction grating. This can be realized, for example, that the diffractive surface of the diffraction grating 2 is designed as a nano-structured aspheric surface or as a free-form surface. With this structure of the spectrometer can z. B. a more compact design can be achieved with a higher temperature stability.

Further can in a further modification of the illustrated principle certain optical effects with the help of others in the beam path provided mirror surfaces can be achieved. So can for example, light losses due to interfacial reflections or scattered light minimizes and the occurrence of temperature-dependent Chromatic aberrations are avoided.

According to one another embodiment of the invention, not shown includes a spectrometer in addition to the diffraction grating a dispersion prism in its beam path, wherein the dispersion direction orthogonal to the dispersion direction of the diffraction grating. For detecting the spectral components of the light or the radiation can a line-shaped detector can be provided.

1

entrance slit

2

diffraction grating

3

field lens

4

lens

5

oscillating mirror

6

lens

7

detector

8th

control device

9

Gitteraperturebene

9a to 9c

pixels

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0167750 [0002]
• - DE 102004046983 A1 [0005]

Cited non-patent literature

• F. Zimmer, H. Grueger, A. Heberer, H. Schenk, H. Lakner, A. Kenda, W. Scherf: "Development of high-efficient NIR scanning gratings for spectroscopic applications", Proceedings of SPIE, Vol. 6114, 611407 (2006), 1-4 [0003]

Claims (10)

Spectrometer for optical spectrometry, comprising a radiation source, an entrance slit ( 1 ), an imaging diffraction grating ( 2 ), downstream in the beam path, an optical field lens ( 3 ), an imaging lens ( 4 ), a vibrating mirror ( 5 ) and at least one further imaging optical element ( 6 ) for imaging the spectrum of the entrance slit ( 1 ) passing radiation onto a single detector element, wherein the oscillating mirror ( 5 ) is provided in a region of the beam path, in which the beam guidance is almost. Spectrometer according to claim 1, characterized at least one of the lenses arranged in the spectrometer has a aspherical or free-form lenses. Spectrometer according to claim 1 or 2, characterized in that the detector ( 7 ) is designed as a punctiform or as a linear detector. Spectrometer according to one of claims 1 to 3, characterized in that for focusing the beam path on the detector ( 6 ) the oscillating mirror ( 5 ) a detector lens ( 6 ), in particular a plano-convex lens or convex lens, is arranged downstream. Spectrometer according to one of claims 1 to 4, characterized in that connected to the detector element and the oscillating mirror control means for detecting the oscillation angle of the oscillating mirror ( 5 ) And to ensure a synchronous detection of the occurring light intensities of the evaluated radiation is provided. Spectrometer according to one of claims 1 to 5, characterized in that the diffraction grating ( 2 ) is formed as a hybrid optical element having a nanostructured aspheric or free-form surface. Spectrometer according to one of claims 1 to 6, characterized in that further imaging mirror surfaces to avoid interface reflections, stray light and / or provided by chromatic aberrations in the optical path of the spectrometer are. Spectrometer according to one of claims 1 to 7, characterized in that the diffraction grating ( 2 ) is designed as a plan or hollow grid. Spectrometer according to one of claims 1 to 8, characterized in that - in addition to the diffraction grating ( 2 ) a dispersion prism is arranged in the beam path whose dispersion direction orthogonal to the dispersion direction of the diffraction grating ( 2 ) - and that a line-shaped detector for detecting the spectral components of the light or the radiation is provided. Spectrometer according to one of claims 1 to 9, characterized in that the entrance slit ( 1 ) Is point or line shaped.