Confocal raman analysing apparatus and method

Abstract

A Raman analysing apparatus comprises an imaging optical system for imaging an object along an optical path to an optical detector, an irradiation optical system for illuminating the object, and a scanning device comprising a spinning pinhole disk. The irradiation optical system directs light onto the scanning device to illuminate the object at a plurality of illumination points. The imaging optical system images Raman scattered light emitted from the object at the illumination points to an intermediate image plane at which the scanning device is located. The imaging optical system may include a spectral filter and/or at least one optical spectral analyser. The apparatus enables high speed confocal Raman imaging and/or high speed confocal Raman spectography to be performed.

1 . A Raman analysing apparatus, the apparatus comprising:
 an optical detector;   an imaging optical system configured to image an object along an optical path to the optical detector;   an irradiation optical system comprising a light source and being configured to illuminate said object by directing light from said light source to the object along at least part of said optical path;   a scanning device comprising a plurality of apertures, the scanning device intersecting said optical path and being movable with respect to the optical path,   wherein said irradiation optical system is configured to direct said light onto said scanning device to illuminate said object at a plurality of illumination points,   and wherein said imaging optical system is configured to image Raman scattered light emitted from said object at said illumination points to an intermediate image plane, said scanning device being located at said intermediate image plane,   and wherein said imaging optical system includes:
 a spectral filter configured to transmit light only in a selected one or more of a plurality of selectable wavelength ranges; and/or 
 at least one optical spectral analyser. 
   
     
     
         2 . The apparatus of  claim 1 , wherein said scanning device comprises a plurality of lenses aligned with said plurality of apertures to focus said light on said apertures. 
     
     
         3 . The apparatus of  claim 1 , wherein said scanning device comprises a rotatable scanning disk, and wherein, preferably, said scanning device comprises a plurality of lenses aligned with said plurality of apertures to focus said light on said apertures, and wherein said scanning device includes a rotatable lens disk in which said plurality of lenses are provided, the lens disk being rotatable with the scanning disk. 
     
     
         4 . The apparatus of  claim 1 , wherein said irradiation optical system includes a Raman bandpass filter, preferably located between said light source and said scanning device. 
     
     
         5 . The apparatus of  claim 1 , wherein said imaging optical system includes a filter, preferably located in said optical path between said scanning device and said optical detector, configured to reject light in a wavelength band corresponding to said light from said light source. 
     
     
         6 . The apparatus of  claim 1 , wherein said light source is a laser light source and is configured to produce a laser beam. 
     
     
         7 . The apparatus of  claim 1 , wherein said optical detector comprises an electronic image sensor, for example comprising a CCD or EMCCD detector, or any other suitable digital image sensor, and may optionally be incorporated into, or may comprise, a digital camera, and/or wherein said optical detector comprises an optical spectral analyser, for example comprising a spectrometer or spectrograph. 
     
     
         8 . The apparatus of  claim 1 , wherein said spectral filter comprises any one of: an optical filter configured to pass light in one or more fixed wavelength bands, or a tuneable optical filter, for example a liquid crystal tuneable filter (LCTF); an acousto-optic tuneable filter (AOTF); a plurality of different filters on a filter wheel or other movable carriage; a plurality of wavelength/angle tuneable filters on a pivotable filter wheel; a plurality of broad-bandpass filters used in conjunction with a Fabry Perot etalon; or a subtractive double monochromator. 
     
     
         9 . The apparatus of  claim 1 , wherein said spectral filter, and/or said at least one optical spectral analyser, is located in the optical path between said scanning device and said optical detector, or wherein said at least one optical spectral analyser serves as said optical detector. 
     
     
         10 . The apparatus of  claim 1 , configured to capture at least one Raman image of said object, each Raman image comprising, or being created from, said Raman scattered light in the selected one or more wavelength ranges. 
     
     
         11 . The apparatus of  claim 1 , further including a beam splitter located in the optical path and being transmissive to one of said light source light and said Raman scattered light, and reflective to the other of said light source light and said Raman scattered light, said imaging optical system being configured to image said object along to the optical detector via the beam splitter, and the irradiation optical system being configured to illuminate said object via the beam splitter, and wherein, optionally, said beam splitter is transmissive to said light source light and reflective to said scattered Raman light, and wherein, optionally, the beam splitter is located between the scanning device and the optical detector, and wherein, optionally, said scanning device comprises a rotatable scanning disk, and wherein said beam splitter is located between said scanning disk and said optical detector, preferably being located adjacent the scanning disk. 
     
     
         12 . The apparatus of  claim 1 , wherein one or more optical polariser is provided in the irradiation optical system, the or each polariser preferably located between the light source and the scanning device. 
     
     
         13 . The apparatus of  claim 1 , wherein one or more polarisation analyser is provided in the imaging optical system, the polarisation analyser preferably being located before the spectral filter or spectral analyser. 
     
     
         14 . The apparatus of  claim 1 , wherein said spectral filter is tuneable, or adjustable, to transmit light only in a selected one or more of a plurality of selectable wavelength ranges. 
     
     
         15 . A Raman analysing method comprising: illuminating an object with excitation light at a plurality of illumination points simultaneously; and imaging Raman scattered light that emanates from the plurality of illuminated points to an optical detector, wherein said illuminating involves directing the excitation light onto a scanning device to illuminate said object at a plurality of illumination points, and wherein said imaging involves imaging the Raman scattered light to an intermediate image plane, said scanning device being located at said intermediate image plane, said method further including: filtering said Raman scattered light to transmit to said optical detector Raman scattered light only in a selected one or more of a plurality of selectable wavelength ranges; and/or performing optical spectral analysis of the Raman scattered light; and optionally filtering light emanating from the plurality of illuminated points to remove said excitation light. 
     
     
         16 . The method of  claim 15 , wherein the filtering involves filtering said Raman scattered light to transmit to said optical detector Raman scattered light in a plurality of different selected wavelength ranges, one range at a time, or one group of more than one range at a time, the method optionally further including creating a composite Raman image comprising, or from, Raman scattered light in each of the selected wavelength ranges. 
     
     
         17 . The method of  claim 15 , further including creating a Raman image comprising, or from, Raman scattered light in the selected one or more of the wavelength ranges, preferably including creating a respective Raman image comprising, or from, Raman scattered light in each of the selected wavelength ranges. 
     
     
         18 . The method of  claim 15 , wherein said illuminating involves scanning a beam of excitation light using a scanning device, and wherein said imaging involves imaging said Raman scattered light to an intermediate image plane, said scanning device being located in said image plane. 
     
     
         19 . The method of  claim 15 , wherein said illumination and said imaging are performed confocally. 
     
     
         20 . A Raman analysing apparatus comprising:
 an optical detector;   an imaging optical system configured to image an object along an optical path to the optical detector;   an irradiation optical system comprising a light source and being configured to illuminate said object by directing light from said light source to the object along at least part of said optical path;   a scanning device comprising a plurality of apertures, the scanning device intersecting said optical path and being movable with respect to the optical path,   wherein said irradiation optical system is configured to direct said light onto said scanning device to illuminate said object at a plurality of illumination points,   and wherein said imaging optical system is configured to capture at least one Raman image of said object, or of a target area of said object, by detecting Raman scattered light from said illumination points in a selected one or more wavelength range.