WO2008037358A1

WO2008037358A1 - Laser scanning microscope and laser scanning microscopy method for measuring diffusely reflected illuminating radiation

Info

Publication number: WO2008037358A1
Application number: PCT/EP2007/007989
Authority: WO
Inventors: Gerald Kunath-Fandrei
Original assignee: Carl Zeiss Microimaging Gmbh
Priority date: 2006-09-28
Filing date: 2007-09-13
Publication date: 2008-04-03
Also published as: DE102006046109A1

Abstract

Laser scanning microscope for measuring diffusely reflected illuminating radiation, with a detector, a detection beam path (DS), which extends from the object under investigation to the detector, a beam splitter which is arranged at an injection location in the detection beam path (DS) and splits the cross section of the detection beam path (DS) at the injection location into a first and a second region, a laser for producing illuminating radiation which is injected via the beam splitter into the first part, which extends from the injection location to the object, of the detection beam path (DS) and is guided to the object, wherein only the illuminating radiation which is incident on the first region is injected into the detection beam path (DS) and wherein only that proportion of the illuminating radiation, which is reflected by the object and travels along the detection beam path (DS) to the beam splitter, that is incident on the second region is injected into the second part, which extends from the beam splitter to the detector, of the detection beam path (DS) in order to detect the diffusely reflected proportion of the reflected illuminating radiation.

Description

Laser Scanning Microscope and Laser Scanninq Microscopy Method for Measuring Diffuse Reflected Illumination Radiation

The following invention relates to a laser scanning microscope and a laser scanning microscopy method for measuring diffusely reflected illumination radiation.

The majority of material surfaces to be detected in materials research and quality control reflect specularly and diffusely, so that they can be described as diffusely reflecting. Since the specular reflection component is usually greater by one or more orders of magnitude than the diffuse reflection component, the diffuse component is greatly outshone and can hardly be evaluated. Furthermore, there is a clearly defined dependence of the inclination of the individual surface section to be detected on the numerical aperture of the microscope in such a way that with inclinations of greater than aresin (NA / 2) a detection is no longer possible, where NA denotes the numerical aperture.

Proceeding from this, it is an object of the invention to provide a laser scanning microscope for measuring diffusely reflected illumination radiation, which solves the difficulties described. Furthermore, a laser scanning microscopy method for measuring diffusely reflected illumination radiation is to be provided.

According to the invention, the object is achieved by a laser scanning microscope for measuring diffusely reflected illumination radiation, comprising a detector, a detection beam path extending from the object to be examined to the detector, a beam splitter arranged at a coupling point in the detection beam path, which cross section of the detection beam path at the coupling point into a first and a second area, a laser for generating illumination radiation, which is coupled via the beam splitter in the coupling point from the coupling to the object extending first part of the detection beam path and guided to the object, wherein only the first Area incident illumination radiation coupled into the detection beam path is and from the reflected from the object illumination radiation, which runs along the detection beam path to the beam splitter, only the portion is coupled into the second part of the detection beam path extending from the beam splitter to the detector, which meets the second region to the diffusely reflected portion of the reflected To detect illumination radiation.

With this microscope, it is possible in a simple manner to fade off the specularly reflected component, so that only diffusely reflected illumination radiation strikes the detector.

In particular, the beam splitter may be formed as a mirror covering the first region. Then, the second region for the diffusely reflected illumination radiation is preferably transmissive.

The beam splitter can also be designed as a mirror covering the second region. In this case, the beam splitter in the first region is preferably transmissive.

In particular, the illumination radiation can be brought into a first polarization state before coupling into the detection beam path by means of a polarizer, wherein in the second part of the detection beam path an analyzer is arranged, which only transmits reflected illumination radiation of a second polarization state, which is preferably orthogonal to the first polarization state, to the detector ,

This makes it possible to shade the specular reflected illumination radiation, which despite the beam splitter in the second part of the detection beam path, so that it does not hit the detector.

In particular, the illuminating radiation impinging on the beam splitter may have a line-shaped cross-section, in which case the first region is also formed linear.

The microscope can detect the object preferably confocal. Thus, an excellent depth resolution is possible and optical sections of the sample can be detected.

Between the beam splitter and the object, a scanner is preferably arranged, which scans the illumination radiation over the object and descares the reflected illumination radiation. Furthermore, a further beam splitter can be arranged between the laser and the beam splitter, which deflects at least one part of the reflected illumination radiation, which is directed by the beam splitter to the laser, onto a further detector. This makes it possible to detect the specularly reflected component (in particular at the same time for the detection of the diffusely reflected component).

The illumination radiation and the reflected illumination radiation preferably have the same wavelength.

The laser scanning microscope can also have further elements or modules which are necessary for the operation of the microscope and are known to the person skilled in the art.

The object is further achieved by a microscopy method for measuring diffusely reflected illumination radiation, is generated in the laser radiation and coupled via a beam splitter in a detection beam path and guided in this to the examining object, the beam splitter, the cross section of the detection beam path at the coupling point in a first and divides a second area, only the incident on the first area illumination radiation is coupled into the detection beam path and of the reflected from the object illumination radiation that runs along the detection beam path to the beam splitter, only the proportion in the extending from the beam splitter to a detector second part of the Detection beam path is coupled, which meets the second region to detect the diffusely reflected portion of the reflected illumination radiation.

With this method, it is possible to hide the specularly reflected portion of the reflected illumination radiation, and thus to easily detect the intensity of the diffusely reflected portion of the illumination radiation, which is usually one to two orders of magnitude smaller than that of the specularly reflected portion.

The beam splitter may be formed as a mirror covering the first region. In this case, the second region is preferably transmissive.

Furthermore, the beam splitter can also be designed as a mirror covering the second region, in which case preferably the first region is transmissive.

In the method, the illumination radiation can be brought into a first polarization state prior to coupling into the detection beam path and can only reflect reflected illumination radiation of a second one in the second part of the detection beam path Polarization state, which is preferably orthogonal to the first polarization state, are forwarded to the detector.

This can be excellently suppressed the specular reflection component.

The incident on the beam splitter illumination radiation may have a line-shaped cross-section, in which case the first region is preferably also formed linear.

The object is preferably detected confocally. Between the beam splitter and the object, a scanner can be arranged, which scans the illumination radiation over the object and descares the reflected illumination radiation.

Furthermore, between the. Laser and the beam splitter may be arranged another beam splitter, which directs at least a portion of the reflected illumination radiation, which is directed by the beam splitter to the laser, to another detector. This makes it possible to detect the specular component at the same time.

In the method, the illumination radiation and the reflected illumination radiation preferably have the same wavelength.

The invention will be explained in more detail with reference to the drawings by way of example. Show it:

1 shows a schematic view of a first embodiment of the laser scanning microscope with the illumination radiation drawn in;

FIG. 2 shows the laser scanning microscope of FIG. 1 with reflected reflected illumination radiation; FIG.

3 shows a cross-sectional representation of the coupling-in point of the detection beam path;

Fig. 4 is an illustration for explaining the specular and diffuse reflection;

5 shows a further illustration for explaining the specular and diffuse reflection;

Fig. 6 shows another embodiment of the laser scanning microscope, and

7 shows a further embodiment of the laser scanning microscope. In the embodiment shown in FIGS. 1 and 2, the laser scanning microscope comprises a laser 1 for generating illumination radiation and, in this order downstream of the laser 1, a polarizer 2, a beam former 3, a deflection mirror 4, a beam splitter 5, a scanner 6 and a lens 7 to direct the illumination radiation of the laser 1 to the sample 8 to be examined.

Furthermore, the laser scanning microscope comprises an analyzer 9, a focusing optics 10 and a detector 11. The beam path from the object 8 to be examined, via the objective 7, the scanner 6, the beam splitter 5, the analyzer 9, the focusing optics 10 to Detector 11 is the detection beam path DS of the laser scanning microscope. The beam path from the laser 1 via the polarizer 2, the beam shaper 3, the deflection mirror 4, the beam splitter 5, the scanner 6, the objective 7 to the object 8 is the illumination beam BS of the laser scanning microscope.

In Fig. 1, only the course of the illumination radiation S is located. The laser 1 emits the illumination radiation S, which here can, for example, have a wavelength in the visible wavelength range and is circularly polarized. The circularly polarized illumination radiation is linearly polarized by means of the polarizer 2 so that the polarization direction extends perpendicular to the plane of the drawing. In the beam former 3, the approximately round beam cross section of the illumination radiation is converted into a line-shaped beam cross section which extends perpendicular to the plane of the drawing, and then directed to the beam splitter 5 via the deflection mirror 4.

The beam splitter 5 is here a line-shaped mirror, as can be seen in particular from the cross-sectional view of FIG. 3, which shows the linear configuration of the mirror 5. The line-shaped mirror divides the cross section of the detection beam path DS, which is circular here, into a first area (namely the area of the mirror 5) and a second area. The second region is composed of the two subregions 12, 13 of the circular cross-section to the right and left of the mirror 5.

The illumination radiation S reflected at the beam splitter 5 impinges on the scanner 6, which deflects the linear illumination radiation S transversely to the line-shaped extension direction over the sample 8, as indicated schematically by the arrow P1.

At the object 8, the illumination radiation is reflected and passes through the lens 7 to the scanner 6, which descares the reflected illumination radiation, and in the direction of Beam splitter 5 hinreflektiert, as shown in Fig. 2, in which the beam path of the reflected illumination radiation RS is located.

The reflected illumination radiation has, as indicated in the schematic illustration of FIG. 4, a specularly reflected component R1 and a diffusely reflected component R2, wherein the intensity of the specularly reflected component R1 is generally one to two orders of magnitude greater than the intensity of the diffusely reflected portion R2. With 14 here the opening cone of the lens 7 is designated.

Due to the specular reflection of specularly reflected R1 runs the same path as the illumination radiation, but only in the opposite direction in the object 8 via the lens 7 and the scanner 6 to the beam splitter 5 and meets there on the mirror 5 and thus in Fig. 2nd reflected to the left to the deflection mirror 4 out.

The proportion of the reflected illumination radiation which does not strike the beam splitter 5 (ie the component which strikes the second region 12, 13 next to the beam splitter 5 in the detection beam path, which is primarily diffusely reflected illumination radiation), does not pass through the beam splitter 5 It is assumed that in the diffuse reflection, the polarization direction of the linearly polarized illumination radiation S is partially rotated, and that the analyzer 9 is set so that it is linearly polarized light which is parallel to the detection beam path DS is polarized to the plane, transmits, a certain proportion of the diffused reflected light R2 passes through the analyzer 9 and is focused on the focusing lens 10 on the detector 11.

The specular reflected light R1, however, retains its polarization direction, so that even if a certain portion of the specular reflected light R1 is not reflected at the beam splitter 5 to the left, but runs to the analyzer 9, then due to the analyzer 9 not further in the detection beam DS can spread and thus does not hit the detector 11.

With the laser scanning microscope shown in FIGS. 1 and 2, it is thus possible to detect only the diffusely reflected illumination radiation RS.

It is also possible with the laser scanning microscope of FIGS. 1 and 2 to detect very large flank angles of the surface topography, as indicated in FIG. 5. There, in turn, the specular component R1 and the diffused component R2 of the reflection are shown. Furthermore, the opening cone 14 of the lens 7 is still located. It can be seen that the specular reflected portion R1 at the surface tilt shown by the laser scanning Microscope can no longer be detected. However, a certain proportion of the diffusely reflected portion R2 is detected and can thus be detected and evaluated, in particular also in comparison with the measurement of the portion of FIG. 4.

FIG. 6 shows a further development of the laser scanning microscope of FIGS. 1 and 2, wherein in FIG. 6 only the reflected illumination radiation RS is shown. Same elements as in Figs. 1 and 2 are designated by the same reference numerals and for their description, reference is made to the above statements.

In contrast to the embodiment of FIGS. 1 and 2, in the embodiment shown in FIG. 6, a coupling-out mirror 15 is arranged between the beam former 3 and the deflection mirror 4, which transmits a part of the reflected illumination radiation guided by the beam splitter 5 to the deflection mirror 4 to a second detector 16 decoupled. The second detector 16 thus mainly measures the specular component R1 of the reflection (and the fraction of the diffuse reflection R2 which runs coaxially with the specularly reflected component R1).

Thus, it is possible to separately detect the specular reflected portion R1 of the reflected illumination radiation and the diffused reflected portion R2.

In Fig. 7, a further embodiment is shown, in turn, the same elements as in Figs. 1 and 2 are designated by the same reference numerals and reference is made to the description thereof to the above statements. In this embodiment, in addition to the beam splitter 5, a further beam splitter 17 is provided, which can be arranged selectively instead of the beam splitter 5 in the detection beam path DS. The beam splitter 17 is e.g. formed as a partially transparent mirror with a cross section which deflects over the entire cross section of the detection beam path DS. Thus, if first the beam splitter 5 is arranged in the position shown in FIG. 7, one can first measure the diffusely reflected component R2 by means of the detector 11. Thereafter, the beam splitter 17 is arranged in the detection beam path DS instead of the beam splitter 5 and the diffusely reflected component R2 can be measured together with the specularly reflected component R1 via the detector 11. This allows further statements about the measured surface to be derived.

In all the described embodiments, it is possible to omit the polarizer 2 and the analyzer 9. In this case, the separation of specular reflected illumination light R1 and diffused reflected illumination light R2 is performed only by the beam splitter 5. Also in this embodiment, the specularly reflected illumination light R1 can be excellently suppressed, so that the diffusely reflected illumination light R2 can be detected. Furthermore, in all the described embodiments, it is possible to focus the illumination radiation S on or in the object 8 at different depths by means of the objective 7, so that optical sections can be detected. An excellent depth resolution (ie resolution in the direction of the propagation direction of the illumination radiation S) can be achieved with confocal detection.

Claims

claims

1. Laser scanning microscope for measuring diffusely reflected illumination radiation, comprising a detector (1 1), a detection beam path (DS), from the object to be examined (8) to the detector

(11) runs, one at a coupling point in the detection beam path (DS) arranged beam splitter (5), the cross section of the detection beam path (DS) at the coupling point in a first

(5) and a second area (12, 13) divides, a laser (1) for generating illumination radiation, which via the beam splitter (5) in the from the coupling point to the object (8) extending first part of the

Detection beam path (DS) coupled and guided to the object (8), wherein only the incident on the first area illumination radiation in the

Detection beam (DS) is coupled and by the object (8) reflected illumination radiation along the

Detection beam path (DS) to the beam splitter (5) runs, only the proportion in the of

Beam splitter (5) to the detector (11) extending second part of the detection beam path (DS) is coupled, which meets the second region (12, 13) to the diffusely reflected

To detect proportion of the reflected illumination radiation.

2. A microscope according to claim 1, wherein the beam splitter is formed as the first region covering mirror.

3. A microscope according to claim 1, wherein the beam splitter is formed as the second region covering mirror.

4. Microscope according to one of the above claims, wherein the illumination radiation prior to coupling into the detection beam path (DS) by means of a polarizer (2) in a first Polarization state is brought and in the second part of the detection beam path (DS), an analyzer (9) is arranged, which passes only reflected illumination radiation of a second polarization state, which is preferably orthogonal to the first polarization state, to the detector (11).

5. Microscope according to one of the above claims, wherein the incident on the beam splitter (5) illuminating radiation has a linear cross-section and the first region (5) is linear.

6. Microscope according to one of the above claims, wherein the object (8) is detected confocally.

7. A microscope according to any one of the above claims, wherein between the beam splitter (5) and the object (8), a scanner (6) is arranged, which scans the illumination radiation on the object (8) and descanted the reflected illumination radiation.

8. Microscope according to one of the above claims, wherein between the laser (1) and the beam splitter (5), a further beam splitter (15) is arranged, the at least a portion of the reflected illumination radiation from the beam splitter (5) to the laser ( 1) is directed to another detector (16) directs.

9. A microscope according to any one of the preceding claims, wherein the illumination radiation and the reflected illumination radiation have the same wavelength.

10. Laser scanning microscopy method for measuring diffuse reflected illumination radiation, wherein

Laser beam generated and coupled via a beam splitter in a detection beam path and is guided in this to the examining object, the beam splitter (5) the cross section of the detection beam path (DS) at the coupling point in a first (5) and a second region (12, 13) divides only the incident on the first area illumination radiation in the detection beam path (DS) is coupled and of the object (8) reflected illumination radiation along the detection beam path (DS) to the beam splitter (5), only the proportion in the of Beam splitter (5) to a detector (11) extending second part of the detection beam path (DS) is coupled, which is incident on the second region (12, 13) to detect the diffusely reflected portion of the reflected illumination radiation.

11. The method of claim 10, wherein the beam splitter is formed as the first region covering mirror.

12. The method of claim 10, wherein the beam splitter is formed as the second region covering mirror.

13. The method according to any one of claims 10 to 12, wherein the illumination radiation is brought into a first polarization state prior to coupling into the detection beam path (DS) and in the second part of the detection beam path (DS) only reflected illumination radiation of a second polarization state, which is preferably orthogonal to first polarization state, is forwarded to the detector (11).

14. The method according to any one of claims 10 to 13, wherein the incident on the beam splitter (5) illumination radiation has a linear cross-section and the first region (5) is linear.

15. The method according to any one of claims 10 to 14, wherein the object (8) is detected confocally.

16. The method according to any one of claims 10 to 15, wherein between the beam splitter (5) and the object (8), a scanner (6) is arranged, which scans the illumination radiation on the object (8) and descanted the reflected illumination radiation.

17. The method according to any one of claims 10 to 16, wherein between the laser (1) and the beam splitter (5), a further beam splitter (15) is arranged, the at least a portion of the reflected illumination radiation from the beam splitter (5) for Laser (1) is directed to another detector (16) directs.

18. The method according to any one of claims 10 to 17, wherein the illumination radiation and the reflected illumination radiation have the same wavelength.