Abstract:
Dispersed wavelength components (38a, 38b) of an incident beam (14) are scanned across a slit aperture (26), and the intensity incident on detector (28) is temporally resolved. The input light (14) includes a reference wavelength component, which provides a timing mark to allow the conversion of measured time differences into wavelength differences. The apparatus may be an optical spectrum analyser with a rotating diffraction grating (18), and the rotation speed may be determined via successive detections of the reference wavelength. Direct measurement of time differences rather than rotation angles, combined with a narrowband reference source, can increase spectral resolution.
Abstract:
An interference filter transmission wavelength scanning photometer wherein the angle of inclination of an interference filter (3) is periodically varied, the wavelength of the light to be transmitted is modulated with the periodical variation centered at the maximum absorption wavelength of the component to be measured, the variation of the intensity of the light transmitted through a sample is extracted by an infrared sensor (11) as an electrical signal, the time between the rise and fall zero cross points of the AC component of the electrical signal is determined by a microprocessor (16), the ratio (full period - 2 x half period)/(full period) is calculated from the full and half periods determined from the determined time, and the concentration of the component to be measured is determined from the variation of the result of the calculation of the ratio, thereby quantitatively determining the component without being influenced by the disturbance coexistent components.
Abstract:
A multichannel imaging spectrometer for airborne geological, geophysical and environmental surveys in a moving vehicle. An optical scanner (123) employs a rotating polygon (20) allowing reduced scan optics with increased data acquisition efficiency. Multiple spectrometers (122) integrally registered allow channelization of the received signal to optimize noise performance in the range from ultraviolet through infrared. Output data is in a form for recording and real time display. A staring mode configuration provides enhanced sensitivity by using a two-dimensional detector array (320, 330) and adjustable mirror orientation. A scanning mode embodiment employs a two-dimensional detector array with time delay integration and three-dimensional storage of temporal spatial data and spectral wavelength and intensity. Thus, all channels are acquired simultaneously, resulting in perfect band-to-band registration with continuous spectral curves over the field of view.
Abstract:
An optical system and method comprising a diffraction grating which consists of diffracting elements spaced from one another by unequal distances. Correction of residual defocusing in the image produced by such a grating is accomplished by translating it along its surface. As one embodiment, a monochromator is constructed in which a self-focusing grating scans the value in wavelength which is transmitted between fixed slits by rotation of the grating about an axis fixed in space. Combined with a translation of the grating along its surface, such a monochromator produces a symmetrical image exactly in focus at the exit slit for all scanned wavelengths.
Abstract:
A system and method for imaging a sample using Raman spectrometry. Optical fibers having opposite first ends and second ends are arranged with the first ends and second ends in respective two-dimensional arrays. The two-dimensional arrays maintain relative positions of the optical fibers to one another from the first ends to the second ends in a way that the first end of each optical fibers of the bundle can simultaneously collect a corresponding Raman signal portion scattered from specific spatial coordinates of the area of the sample. The so-collected Raman signal portions are propagated towards the corresponding second end, from which are outputted and detected simultaneously using an array of detectors.
Abstract:
A compact spectrometer includes an excitation light source configured to generate excitation light and arranged to illuminate a spot on a sample. A dispersive element includes at least one movable component and spatially separates output light emanating from the sample in response to the excitation light into a plurality of different wavelength bands. A moveable component of the dispersive element causes the plurality of different wavelength bands of the output light to be scanned across a detector. The detector includes at least one light sensor that senses the wavelength bands of the output light and generates an output electrical signal in response to the sensed output light.
Abstract:
A spectral imaging system includes an autocorrelator to generate different autocorrelations when the moving reflector in the autocorrelator is at different positions so as to reconstruct spectral images. The system also includes a position measurement system to measure the actual positions of the moving reflector when autocorrelations are taken. These actual locations, instead of the desired locations in conventional methods, are then used to reconstruct the spectral image. This approach can address the misalignment of the moving reflector from its desired location (due to external disturbances, slow actuator dynamics, and other factors) in conventional spectral imaging techniques and allow the development of high-resolution, high-stability, portable imaging spectrometers for the general public.