Detection system for Raman scattering employing holographic diffraction
First Claim
1. A Raman scattering detector comprising:
- a source of collimated, substantially monochromatic light along a primary optical axis;
a first right angle prism having a first right angle face disposed perpendicular to said primary optical axis, a second right angle face disposed parallel to said primary optical axis, and an oblique face;
a holographic optical element disposed parallel to said oblique face of said first right angle prism, said holographic optical element having embedded therein regions of alternating indices of refraction for passing said monochromatic light substantially undiffracted while diffracting light at the wavelengths of expected Raman scattered light through an angle of approximately 90 degrees;
a second right angle prism having an oblique face disposed parallel to said holographic optical element, and a first right angle face disposed perpendicular to said primary optical axis;
a sample cell disposed on said primary optical axis beyond said first right angle face of said second right angle prism for holding a sample substance to be irradiated;
a concentrating lens disposed perpendicular to said primary optical axis between said first right angle face of said second right angle prism and said sample cell for concentrating said monochromatic light on the sample within said sample cell and for collimating Raman scattered light parallel to said primary optical axis;
a focussing lens disposed parallel to said second right angle face of said first right angle prism having a secondary optical axis perpendicular to said primary optical axis for focussing Raman scattered light diffracted by said holographic optical element at a focal plane; and
at least one photosensitive detector disposed on said focal plane of said focussing lens at a location off said secondary axis.
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Abstract
The Raman scattering detector of this invention includes a source of collimated monochromatic illumination, a cube formed of two right angle prisms, a holographic optical element disposed between the prisms, a concentrating lens, a focusing lens and one or more photo detectors. The illuminating beam passes through the cube and is concentrated by the concentrating leans to a sample. Scattered light returned to the concentrating lens is substantially collimated upon return to the cube. The holographic optical element diffracts light at desired Raman wavelengths approximately 90 degrees without substantially affecting the original wavelength. The holographic optical element further disperses light at desired Raman wavelengths permitting them to be separated. The diffracted and dispersed wavelengths are focused on one or more detectors by the focusing lens.
60 Citations
16 Claims
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1. A Raman scattering detector comprising:
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a source of collimated, substantially monochromatic light along a primary optical axis; a first right angle prism having a first right angle face disposed perpendicular to said primary optical axis, a second right angle face disposed parallel to said primary optical axis, and an oblique face; a holographic optical element disposed parallel to said oblique face of said first right angle prism, said holographic optical element having embedded therein regions of alternating indices of refraction for passing said monochromatic light substantially undiffracted while diffracting light at the wavelengths of expected Raman scattered light through an angle of approximately 90 degrees; a second right angle prism having an oblique face disposed parallel to said holographic optical element, and a first right angle face disposed perpendicular to said primary optical axis; a sample cell disposed on said primary optical axis beyond said first right angle face of said second right angle prism for holding a sample substance to be irradiated; a concentrating lens disposed perpendicular to said primary optical axis between said first right angle face of said second right angle prism and said sample cell for concentrating said monochromatic light on the sample within said sample cell and for collimating Raman scattered light parallel to said primary optical axis; a focussing lens disposed parallel to said second right angle face of said first right angle prism having a secondary optical axis perpendicular to said primary optical axis for focussing Raman scattered light diffracted by said holographic optical element at a focal plane; and at least one photosensitive detector disposed on said focal plane of said focussing lens at a location off said secondary axis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10)
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9. A Raman scattering detector comprising:
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a source of collimated, substantially monochromatic light along an primary optical axis; a first prism having a first face disposed perpendicular to said primary optical axis, an oblique face, and a convex face disposed substantially parallel to said primary optical axis, said convex face forming a focussing lens disposed parallel to said primary optical axis having a secondary optical axis perpendicular to said primary optical axis for focussing Raman scattered light diffracted by said holographic optical element at a focal plane; a holographic optical element disposed parallel to said oblique face of said first right angle prism, said holographic optical element having embedded therein regions of alternating indices of refraction for passing said monochromatic light substantially undiffracted while diffracting light tt the wavelengths of expected Raman scattered light through an angle of approximately 90 degrees; a sample cell disposed on said primary optical axis beyond said first prism for holding a sample substance to be irradiated; a second prism disposed between said holographic optical element and said sample cell having an oblique face disposed parallel to said holographic optical element, and a convex face disposed substantially perpendicular to said primary optical axis, said convex face forming a concentrating lens disposed perpendicular to said primary optical axis for concentrating said monochromatic light on the sample within said sample cell and for collimating Raman scattered light parallel to said primary optical axis; and at least one photosensitive detector disposed on said focal plane of said focussing lens at a location off said secondary axis. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification