Computational polarimetric and multispectral imaging with a variable filter mask

We report on progress made in developing a polarimetric and multispectral imaging (MSI) camera that uses a coded filter mask to record spectral data on either a single frame or only a few frames depending on the design of the mask and the application. The design uses commercially available variable filters and beamsplitters to record spectral data simultaneously on a focal plane array, thus negating the need for scanning mechanisms or dispersive optical elements. The data rate depends on the design of the filter mask, pixel resolution, relative motion between target and camera, and the frame rate. The polarimetric data is recorded on a single frame thus eliminating latency. Multispectral data may be recorded on a few frames or a single frame, thus reducing the need for many multi-frame acquisitions. An optimum mask design matched to the imaging lens and focal plane array resolution, allows an object to be detected against spectral clutter or background on a single pixel. Thus a spatially resolved image is not required, alleviating the need for high magnification which would be a practical limitation where compact optical systems are required. The proof-of-principle is reported that uses a 1D variable filter mask to provide spectra of resolved target images in the near field for the visible spectrum. Test data are presented that show the potential for the concept and how it is readily extended to use a 2D mask in a modified design.