Collection of micromirror-modulated light in the single-pixel broadband hyperspectral microscope.

A digital micromirror device (DMD) serves in a significant part of computational optical setups as a means of encoding an image by the desired pattern. The most prominent is its usage in the so-called single-pixel camera experiment. This experiment often requires an efficient and homogeneous collection of light from a relatively large chip on a small area of an optical fiber or spectrometer slit. Moreover, this effort is complicated by the fact that the DMD acts as a diffractive element, which causes severe spectral inhomogeneities in the light collection. We studied the effect of light diffraction via a whiskbroom hyperspectral camera in a broad spectral range. Based on this knowledge, we designed a variety of different approaches to the light collection. We mapped the efficiency and spectral homogeneity of each of the configuration, namely, its ability to couple the light into commercially available fiber spectrometers working in the visible and infrared range (up to 1900 nm). We found the integrating spheres to provide homogeneous light collection, which, however, suffers from very low efficiency. The best compromise between the performance parameters was provided by a combination of an engineered diffuser with an off-axis parabolic mirror. We used this configuration to create a computational microscope able to carry out hyperspectral imaging of a sample in a broad spectral range (400 nm-1900 nm). We see such a setup as an ideal tool to carry out spectrally resolved transmission microscopy in a broad spectral range.