Abstract: A fiber-optic probe uses imaging optics between the remote ends of the excitation and collection fibers and the sample under investigation to enhance working distance and efficiency. In one embodiment a plurality of collection fibers are disposed circumferentially around a central excitation fiber, enabling a conventional focussing lens arrangement to be used for imaging purposes. The assembly may optionally include a rotationally symmetric diffraction grating to cause the excitation energy to assume an annulus superimposed over the image of the collection fibers. The excitation and collection fiber may alternatively be physically spaced apart from one another sufficient to permit one or more optical elements to be disposed in either or both of the excitation and collection paths, depending upon the application.

Abstract: The collection of spectral information is enhanced through the formation of multiple zones of excitation and emission. In one embodiment, a plurality of the zones are located within a sample substance, thereby increasing the efficiency of sample spectrum collection. In another embodiment, a reference substance is positioned so as to enclose at least one of the excitation/collection zones. The reference substance adds a known spectrum to the collection path, enabling analytical instrumentation to compare the sample and reference spectra for calibration purposes. In a further embodiment, one of the zones may be positioned within a sealed volume, and compositional changes in the sealed volume may be detected and used for leak-detection purposes.

Abstract: A dispersive grating, preferably in the form of a volume-phase holographic optical element, or HOE, is used as a beam combiner in an optical measurement probe of the type used to analyze induced radiative effects such as Raman or fluorescence detection. Although a reflective grating may be used, a transmission grating of holographic derivation is used in the preferred embodiment. Although the grating may define an area substantially equivalent to the cross-section or aperture of the collection path, a grating which consumes a fraction of the collection aperture may instead be utilized, thereby allowing collected light to pass around the grating to further enhance the efficiency of detection. As a further advantageous option, the grating may be fabricated with `power,` that is, with the capability of collimating excitation energy that has been focused onto the grating surface.

Abstract: Methods and apparatus for synchronous spectral line imaging are disclosed for use in conjunction with any of a number of radiative analysis techniques such as Raman or fluorescence detection. Light emitted points on a sample are separated into wavelength components and directed onto a two-dimensional image sensor such that the wavelength components impinge along one dimension of the sensor. The other dimension of the sensor is used in conjunction with spatial position relative to the sample, with at least certain of the steps being repeated for the different sample points so as to form the spectral line image. In terms of apparatus, the invention preferably utilizes at least one optical fiber having an input end to receive the light emitted by the sample and an output end to deliver the emitted light to the two-dimensional image sensor. The use of a flexible optical fiber facilitates the movement of the light received from the sample, movement of the received light relative to the sensor, or both.

Abstract: A multimode optical fiber is used in a confocal light-collection arrangement. A confocal aperture is supported in intimate proximity with respect to the first end of the fiber, preferably within two core diameters from the first end of the fiber. In the preferred embodiment, the confocal aperture is formed directly onto the first end of the fiber using, for example, photolithography or photoablation of a thin metallic film adhered directly to the light-collection end of the multimode fiber.

Abstract: A holographic probe facilitates the measurement of radiative effects such as Raman scattering or fluorescence of a remotely disposed sample. Improving upon prior-art techniques, the probe teaches a substantially in-line path between the sample and an output optic wherein a narrowband reflective element, preferably holographically recorded, is used to fold excitation energy from an illumination path into the collection path and reject any Rayleigh scattering received from the sample. The improved configuration further allows a dispersive filtering element to be placed in the illumination path, which may be used in conjunction with spatial filtering to reject non-excitation wavelengths.