Spectrometer system with IR microscope and electronically switchable detectors

Abstract

A spectrometer system (1) comprising an IR (infrared) spectrometer (2) and an IR microscope (3), wherein a sample (42) and a first detector (21; 31) are provided in the IR microscope (3), wherein the IR microscope (3) is designed such that during measurement, the sample (42) is imaged on the first detector (21; 31) via an intermediate focus (44), is characterized in that at least one second detector (24, 25; 33) is provided whose detector surface (26, 27; 34) extends parallel to the detector surface (22; 32) of the first detector (21; 31), the detector surface (26, 27; 34) of the at least one second detector (24, 25; 33) is at least 5 times larger than the detector surface (22; 32) of the first detector (21; 31), and the first (21; 31) and the at least one second detector (24, 25; 33) are disposed directly next to each other, wherein the detector surface (26, 27; 34) of the at least one second detector (24, 25; 33) largely surrounds the detector surface (22; 32) of the first detector (21, 31), and the first detector (21; 31) can be read out independently of the at least one second detector (24, 25; 33). The inventive spectrometer system yields a good signal-to-noise ratio both for large and small selected sample areas.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic perspective view of an inventive spectrometer system with IR spectrometer and IR microscope;

FIG. 2 shows a schematic top view of a detecting arrangement with a central detector surface of a first detector and two second detectors each having a C-shaped detector surface, for an inventive spectrometer system;

FIG. 3 shows a schematic top view of a further detecting arrangement with a central detector surface of a first detector which is disposed on the detector surface of a second detector, for an inventive spectrometer system;

FIG. 4 shows a schematic view of the path of rays in an IR microscope for an inventive spectrometer system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a schematic perspective view of an inventive spectrometer system 1 from the outside.

The spectrometer system 1 comprises an infrared spectrometer 2 which houses an infrared source (not shown) and an interferometer (not shown).

An IR microscope 3 is directly connected to the IR spectrometer 2, such that an IR light beam of the infrared spectrometer 2 can be guided into the IR microscope 3 and used therein.

The IR microscope 3 has a sample plate 4 which can be horizontally displaced in the x and y directions and also vertically in the z direction, either manually or by electromotive control. A sample to be investigated may be disposed on the sample plate 4.

A detection arrangement comprising a first IR detector and at least one second IR detector is provided in the IR microscope 3 (explained in FIGS. 2 and 3). The path of rays of the IR light beam in the IR microscope 3 is explained in more detail in FIG. 4.

The IR microscope 3 also comprises a light-optical system for visible light. An enlarged sample can also be observed with the human eye via double ocular 5. An optical component, in particular a collimator or scale template is thereby preferably provided in a light-optical intermediate focus, which light-optically marks the sample area which is selected for IR spectroscopy. The sample may also be observed beyond the selected sample area using the scale template (e.g. a glass plate with lines).

FIG. 2 shows a schematic top view of a detecting arrangement 20 for an IR microscope for the invention.

The detecting arrangement 20 comprises a first IR detector 21 which has an approximately square, flat detector surface 22. Metallic contacts 23a, 23b are provided on the upper and lower edges of the detector surface 22, via which the detector 21 can be read out.

The detecting arrangement 20 moreover comprises two second detectors 24, 25, each having flat C-shaped detector surfaces 26, 27. The arms of the Cs face each other, thereby encompassing an inner space. The detector surface 22 of the first detector 21 is disposed in this inner space. The detector surfaces 26, 27 of the second detectors 24, 25 may also be regarded as rectangular, each comprising one recess A that faces the center of the detecting arrangement 20, wherein the detector surface 22 of the first detector 21 is disposed in the space defined by the recesses A. The upper and lower edges of each detector surface 26, 27 of the second detectors 24, 25 are connected to metallic contacts 28a, 28b, 29a, 29b, via which the second detectors 24, 25 can be read out.

The detectors 21, 24, 25 are disposed on a carrier 20a. The detector surfaces 22, 26, 27 are at the same level in the z direction (perpendicular to the plane of the drawing).

In the illustrated case, the detector surface 22 of the first detector 21 is approximately 1/25 of the overall detector surface of the two second detectors 24, 25. When the sample area which is imaged on the detector arrangement 20 substantially only illuminates the detector surface 22 of the first detector 21, only the first detector 21 is read out and evaluated in accordance with the invention, thereby obtaining a good SNR. If, however, a larger sample area is imaged which also illuminates the detector surfaces 26, 27 of the second detectors 24, 25, the first detector 21 and the second detectors 24, 25 can be read out and the detected signals can be integrally evaluated. Only very little information is lost, namely in correspondence with the portion of the sample image (or selected sample area) which passes the detectors 21, 24, 25 and e.g. impinges directly on the carrier 20a in the intermediate space between the detectors 21, 24, 25.

A typical edge length of the first detector surface 21 is 20 μm to 200 μm and typical outer dimensions of the overall detector surface of the second detectors 24, 25, are 100μ to 1000 μm.

FIG. 3 shows another inventive design of a detecting arrangement 30 comprising a first detector 31 and a second detector 33.

The first detector 31 is disposed on the upper side of the detector surface 34 of the second detector 33, i.e. glued, thereby shadowing a small part of the detector surface 34 of the second detector 33. The remaining free part of the detector surface 34 of the second detector 33 is approximately 8 times larger than the detector surface 32 of the first detector 31.

The first detector 31 is contacted by thin wires 35 to minimize shadowing of the second detector 33 by the contacts of the first detector 31.

The first detector 31 and the second detector 33 are both formed as HgCdTe detectors and disposed in a common refrigerator housing 36, which may be cooled e.g. using liquid nitrogen. Alternatively, other materials may also be used as detector (e.g. InSb) or the type or material of the first detector 31 may differ from that of the second detector 33.

FIG. 4 schematically shows the IR path of rays in an IR microscope in accordance with the invention in transmission operation.

IR radiation (not shown) that is incident on a capacitor 41 is focussed onto a sample 42. The sample 42 may be displaced perpendicularly to the path of rays in x and y direction in order to bring a certain location on the sample 42 into the center of the path of rays.

The sample 42 is imaged on an intermediate focus 44 using an objective 43 (or another suitable optical component). A variable collimator 45 is disposed on the intermediate focus 44 for shadowing a part of the sample 42 which is not of interest, thereby selecting a sample area of interest. The size of the selected sample area can be varied by the variable collimator diameter of the variable collimator 45. Variation of the collimator diameter would appear as a change in separation between the two side parts of the variable collimator 45 (shown in cross-section).

When the variable collimator 45 is suitably designed, the geometry of the selected sample area can also be varied.

The intermediate focus 44 and thereby also the variable collimator 45 and the sample 42 (or the selected sample area of the sample 42) are imaged on a detecting arrangement 47 using an objective 46 (or another suitable optical component). In accordance with the invention, the detecting arrangement 47 comprises one first detector and at least one second detector with electronic switching therebetween. The path of rays need not be changed thereby. The mutually surrounding approximately coplanar arrangement of the detectors requires, in particular, no mechanical switching over between the detectors.

In summary, the invention proposes the use of a first and at least one second detector in substantially the same plane (detection plane) in a spectrometer system with IR microscope, wherein two second detectors together have a considerably larger detector surface than the first detector and the totality of the second detectors with its detector surface surrounds the detector surface of the first detector. Depending on the size of the sample area to be imaged, a detector or a combination of detectors having the best SNR may be used.

Claims

1. A spectrometer system for examining a sample, the system comprising: an IR (infrared) spectrometer;an IR microscope within which the sample is disposed;a first detector disposed in said IR microscope, said IR microscope being designed such that, during measurement, the sample is imaged on said first detector via an intermediate focus;at least one second detector having a detector surface which extends parallel to a detector surface of said first detector, said detector surface of said at least one second detector being at least 5 times larger than said detector surface of said first detector, said first and said at least one second detector being disposed directly next to each other, wherein said detector surface of said at least one second detector largely surrounds said detector surface of said first detector; andmeans for reading out said first detector independently of said at least one second detector.

2. The spectrometer system of claim 1, wherein said detector surface of said at least one second detector is at least 10 times or at least 25 times larger than said detector surface of said first detector.

3. The spectrometer system of claim 1, wherein said first and said at least one second detector are disposed in a common refrigerator housing.

4. The spectrometer system of claim 3, wherein said housing is cooled using liquid nitrogen.

5. The spectrometer system of claim 1, wherein said first detector and/or said at least one second detector is/are a HgCdTe detector.

6. The spectrometer system of claim 1, wherein said IR microscope is designed for reflection operation, transmission operation, and/or for ATR (weakened total reflection) operation.

7. The spectrometer system of claim 1, wherein said IR spectrometer is designed as an FTIR (Fourier transformation infrared) spectrometer.

8. The spectrometer system of claim 1, wherein said first detector is disposed in a recess of said detector surface of said at least one second detector.

9. The spectrometer system of claim 1, wherein said first detector is disposed between two second detectors.

10. The spectrometer system of claim 9, wherein said two second detectors are substantially C-shaped and face each other.

11. The spectrometer system of claim 1, wherein said first detector is disposed on said detector surface of said second detector.

12. The spectrometer system of claim 1, wherein a collimator is disposed at said intermediate focus.

13. The spectrometer system of claim 12, wherein said collimator is designed as a variable collimator having a variable collimator diameter.