Abstract:
A method for conducting FCS measurements includes providing a sample volume, emitting a target light having a first wavelength from a target light source, and marking an FCS volume in the sample volume with the target light by directing the target light onto the sample volume. An illuminating light having a second wavelength is emitted from an illuminating light source, the second wavelength being different than the first wavelength, and the illuminating light is directed onto the sample volume.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This patent application is a continuation of copending U.S. patent application Ser. No. 12/088,639, filed Mar. 28, 2008, which is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/EP2006/066861, filed Sep. 28, 2006, and claims benefit of German Patent Application No. 10 2005 046 510.2, filed Sep. 29, 2005, all three of which are hereby incorporated by reference in their entirety herein. The International Application was published in German on Apr. 5, 2007 as WO 2007/036559 A1 under PCT Article 21(2). 
    
    
     FIELD 
     The invention relates to a microscope system for Fluorescence Correlation Spectroscopy (FCS) measurements, and in particular, to a microscope system for conducting FCS measurements. 
     BACKGROUND 
     European Patent EP 0 941 470 describes a fluorescence correlation spectroscopy module for a microscope. The FCS module can additionally be connected to a microscope of any desired design. Fluorescence correlation spectroscopy allows the investigation of molecular dynamic processes to be studied. For this purpose, the particles contained in solution are doped with fluorescent dyes, and these dyes are then excited by light of a particular wavelength. The excitation light coming from a laser is coupled into the module via a flange joint for an optical waveguide. In the FCS module known from prior art, it is difficult to align the FCS detection volume with the sample area, which is to be investigated. 
     SUMMARY 
     The present invention provides a method of conducting FCS measurements. The method includes providing a sample volume, emitting a target light having a first wavelength from a target light source, and marking an FCS volume in the sample volume with the target light by directing the target light onto the sample volume. An illuminating light having a second wavelength is emitted from an illuminating light source, the second wavelength being different than the first wavelength, and the illuminating light is directed onto the sample volume. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, the subject matter of the invention is illustrated schematically, and will be described in the following with the aid of the figures, in which: 
         FIG. 1  shows a schematic illustration of a first embodiment of the invention; and 
         FIG. 2  shows a schematic illustration of a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to a microscope method which can be used to reliably perform the alignment with the sample volume to be investigated. This can be achieved by a microscope system comprising the features described below. 
     In accordance with one embodiment of the invention the microscope system for conducting Fluorescence Correlation Spectroscopy (FCS) measurements can be provided with a target light source for marking an FCS volume. Here, the light of the target light source can be also directed onto the sample volume via the plurality of optical elements. The wavelength of the first light source preferably differs from the wavelength of the target light source. 
     A combining element can be provided which combines the illuminating light of the first light source with the light of the target light source to form a common beam path. The light of the target light source preferably has a longer wavelength than the illuminating light of the first light source. 
     In accordance with a further aspect of the present invention, the light of the target light source can have a wavelength that is in the region of red light. In the same way, the light of the target light source can have a wavelength that is in the region of IR light. In the case of IR light, a camera is provided which registers the IR light and converts it into an image visible to the user. Furthermore, the target light source is preferably provided with a correcting optics in order to compensate chromatic aberrations due to the different wavelengths of the first light source and the target light source. 
     In accordance with yet a further feature of the one embodiment of the present invention, the first light source and/or the target light source can include a laser. 
     In a further embodiment, the microscope is provided with an optical fiber into which the illuminating light of the at least first light source and the light of the target light source can be coupled in order to achieve the collinearity of the illuminating light and the light of the target light source. In this case, the combining element can include a beam splitter. Alternatively, the combining element can include an AOTF, an AOBS or an AOM. 
     Further advantageous refinements of the invention can be found in the discussion below . 
       FIG. 1  schematically describes a microscope system  1  for conducting FCS measurements. The microscope system  1  is provided with at least one first light source  3  which emits illuminating light which is directed onto a sample volume  5  or a sample. Additionally, a target light source  7  for marking the FCS volume  5  is provided. The target light source  7  emits light  6 , which is also directed onto the FCS volume. The wavelength of the illuminating light  2  of the first light source  3  differs from the wavelength of the light  6  of the target light source  7 . The light  2  from the illuminating light source  3  and the light  6  from the target light source  7  are combined by a combining element  9  to form a common, collinear beam path. In this case, the combining element  9  can be designed to include a beam splitter. Optionally, the combining element  9  can include an AOTF, an AOBS or an AOM. A correcting optics  10  is provided between the target light source  7  and the combining element  9 , in order to compensate chromatic aberrations due to the different wavelengths of the light  2  of the first light source  3  and the light  6  of the target light source  7 . The light  2  of the first light source  3  and the light  6  of the target light source  7  is directed onto the sample volume  5  or the volume via a plurality of optical elements  12  and a microscope optics  14 . The sample volume  5  or sample is preferably provided at least on an X-Y table  16 , in order thereby to change the sample volume with respect to the position of the illuminating light. The sample volume  5  is excited to fluoresce due to the illumination by the first light source  3 , so that the sample volume  5  emits a detection light  15 , which is also directed onto the detector  18  via the microscope optics  14  and the optical elements. The light  6  of the target light source  7  has a longer wavelength than the illuminating light  2  of the first light source  3 . In a first embodiment, the light  2  of the target light source  3  has a wavelength lying in the region of red light. The location of the light  6  of the target light source  7  on the sample volume  5  can therefore be observed directly and visually by a user  24 . If the light  6  of the target light source  7  lies in the wavelength region of IR light, a camera  22  is provided which produces an image for the user  24 , so that the latter can recognize the location of the illuminating light  25  in the sample volume  5 . 
       FIG. 2  shows a further embodiment of the microscope system  1 . Arranged downstream of the combining element  9  is an optical fiber  30  into which the illuminating light  2  of the at least first light source  3  and the light  6  of the target light source are coupled. The collinearity of the illuminating light is achieved by coupling the illuminating light  2  of the light  6  of the target light source  7  into the optical fiber  30 . This ensures that the light  6  of the target light source  7  and the illuminating light  2  of the at least first light source  3  impinge on a shared impingement location  25  in the sample volume  5  or in the sample. The optical fiber  30  can be provided with a coupling-in optics  31  and a coupling-out optics  32 .