Multispectral imager using band pass optical filters and image illumination correction



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Commercially available multispectral or hyperspectral imaging systems are designed to capture images, at predefined wavelength intervals. Various mechanisms are implemented for changing the wavelength intervals of light used for capturing spectral images, and any variations in these frequency intervals require major alterations. Dispersion of light is carried out either by diffraction gratings or by electronically tunable filters. Apparatus with diffraction grating are inexpensive but have slow response time. Electronically tunable filters have quick response time but make the apparatus expensive. Imaging systems where optical filters are mounted on a rotating disc to capture hyperspectral images have a predefined utility because there is no means to select or adjust the filters that are placed on the disc for an given experiment. The proposed approach includes the use of step up rings to attach the optical filters with threaded c-mount attachments to the holes in a metal disc. The use of step up rings to mount the optical filters provides a way to replace filters effortlessly. As a result, the system has additional research functionality to be used as a test structure to evaluate the performance of the filters, based on their response and the selection of central frequency according to the requirements of an experiment. The precision processing of light required while using diffraction gratings or tunable filters can be avoided by the use of optical filters. The assembly with optical filters does not require precise control on the disc, because positioning the filters in front of the camera. The proposed assembly also provides a prototype that can be improved to accelerate the process of image acquisition, which will make the apparatus faster than the one with diffraction grating and less expensive than the one with tunable filters.