Abstract:
An Echelle spectrometer arrangement (10) with internal order separation contains an Echelle grating (34) and a dispersing element (38) for order separation so that a two-dimensional spectrum having a plurality of separate orders (56) can be generated, an imagine optical system (18, 22, 28, 46), a flat-panel detector (16), and predispersion means (20) for predispersing the radiation into the direction of traverse dispersion of the dispersion element (38). The arrangement is characterized in that the predispersion means (20) comprise a predispersion element which is arranged along the optical path behind the inlet spacing (12) inside the spectrometer arrangement. The imaging optical system is designed in such a manner that the predispersed radiation can be imaged onto an additional image plane (24) which does not have any boundaries in the predispersion direction and which is arranged along the optical path between the predispersion element (20) and the echelle grating (34). Optical means (20, 68) in the area of the predispersed spectrum are arranged to influence the spatial and/or the spectral beam density distribution on the detector (16).
Abstract:
A zoned order sorting filter for a spectrometer in a semiconductor metrology system is disclosed with reduced light dispersion at the zone joints. The order sorting filter comprises optically-transparent layers deposited underneath, or on top of thin-film filter stacks of the order sorting filter zones, wherein the thicknesses of the optically-transparent layers are adjusted such that the total optical lengths traversed by light at a zone joint are substantially equal in zones adjacent the zone joint. A method for wavelength to detector array pixel location calibration of spectrometers is also disclosed, capable of accurately representing the highly localized nonlinearities of the calibration curve in the vicinity of zone joints of an order sorting filter.
Abstract:
An individualized modeling equation for predicting a patient's blood glucose values is generated as a function of non-invasive spectral scans of a body part and an analysis of blood samples from the patient, and is stored on a central computer. The central computer predicts a blood glucose value for the patient as a function of the individualized modeling equation and a non-invasive spectral scan generated by a remote spectral device. If the spectral scan falls within the range of the modeling equation, the predicted blood glucose level is output to the patient. If the spectral scan falls outside the range of the modeling equation, regeneration of the model is required, and the patient takes a number of noninvasive scans and an invasive blood glucose level determination. The computer regenerates the individualized modeling equation as a function of the set of spectral scans and corresponding blood glucose values.
Abstract:
A hemispherical detector comprising a plurality of photodetectors arranged in a substantially contiguous array, the array being substantially in the shape of a half-sphere, the half-sphere defining a closed end and an open end, the open end defining a substantially circular face. Also provided is a method for constructing a hemispherical detector comprising the steps of making a press mold of the desired shape of the hemispherical detector, pouring a material into the press mold to form a cast, finishing the cast to remove any defects, coating the cast with a coating material, and attaching a plurality of photodetectors to the cast.
Abstract:
A method and apparatus for the spectrochemical analysis of a sample in which a solid state array detector (82) is used to detect radiation (62) of spectrochemical interest. The invention involves the use of a shutter (72) adjacent the entrance aperture (70) of a polychromator (74-80) to expose the detector (82) to the radiation (62) for varying lengths of time whereby for short duration exposure times charge accumulation in elements (i.e. pixels) of the detector (82) due to high intensity components of the radiation is limited and for longer exposure times charge accumulation in elements (pixels) of the detector (82) due to feeble intesity components of radiation (62) is increased. This ensures that each reading of the detector (82) includes at least one exposure in which the amount of charge accumulated at each wavelength of interest is neither too little or too great. The problems of feeble radiation components not being accurately measurable and of high intensity radiation components exceeding the charge carrying capacity of elements (pixels) of the detector (82) are thereby able to be avoided. An attenuator (90) may be placed between the radiation source (60) and the detector (82) to permit longer exposure times to be used for very high intensity radiation.
Abstract:
A spectrometric instrument passes flashing light through a sample and has a linear detector operated by the computer to integrate signals for an established number of flashes to obtain an integrated unit of the signal data, from which spectral information is displayed on a monitor. Over a full spectral range, the established number is determined as that which effects a highest peak height proximately below a preselected maximum, and light source voltage is adjusted to bring the peak height closer to the maximum. For a narrower spectral range, an operating number of flashes for a unit is increased above the established number to accommodate a lower highest peak in the range. Wavelength calibration uses peaks in the light source. Corrections are made for stray light and non-linearity of detector response. Calculation of auxiliary information derived from input of auxiliary data through a touch screen is displayed on the monitor.
Abstract:
A small spectrograph containing no moving components and capable of providing high resolution spectra of the mid-infrared region from 2 microns to 4 microns in wavelength. The resolving power of the spectrograph exceeds 20,000 throughout this region and at an optical throughput of about 10.sup.-5 cm.sup.2 sr. The spectrograph incorporates a silicon immersion echelle grating operating in high spectral order combined with a first order transmission grating in a cross-dispersing configuration to provide a two-dimensional (2-D) spectral format that is focused onto a two-dimensional infrared detector array. The spectrometer incorporates a common collimating and condensing lens assembly in a near aberration-free axially symmetric design. The spectrometer has wide use potential in addition to general research, such as monitoring atmospheric constituents for air quality, climate change, global warming, as well as monitoring exhaust fumes for smog sources or exhaust plumes for evidence of illicit drug manufacture.
Abstract:
A spectrometer comprises a tunable interferometer for producing a monochromatic continuous image at an image plane and including two mirrors having substantially parallel surfaces and an adjustable spacing therebetween, a radiation detector located at the image plane for recording the image, a filter arrangement for allowing at least one predetermined range of wavelengths to pass to the detector, and a lens arrangement for collecting radiation and limiting radiation incident on the interferometer to an angle which is substantially perpendicular to the substantially parallel surfaces of the two mirrors.
Abstract:
A double-pass scanning monochromator for use in an optical spectrum analyzer includes an input optical fiber for emitting an input light beam, a diffraction grating for diffracting the input light beam to produce a spatially dispersed light beam, a slit for passing a selected portion of the dispersed light beam, a motor for rotating the diffraction grating, a shaft angle encoder for sensing grating position, and an output optical fiber. The light that passes through the slit is directed to the diffraction grating and is recombined by the diffraction grating to produce an output light beam. The light beam to be analyzed is incident on the diffraction grating during first and second passes. A polarization rotation device rotates the polarization components of the light beam by 90.degree. between the first and second passes so that the output of the monochromator is independent of the polarization of the input light beam. The output optical fiber is translated by a micropositioning assembly in a plane perpendicular to the output light beam during rotation of the diffraction grating to automatically track the output light beam and to provide optical chopping.