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Digital micromirror device (DMD) serves in a major part of computational optical setups as a means of encoding an image by a desired pattern. The most prominent is its usage in the so-called single-pixel camera experiments, where light reflected from a DMD is collected onto a single-pixel detector. This often requires efficient and homogenous collection of light from a relatively large chip on a small area of an optical fiber or spectrometer slit. This effort is moreover complicated by the fact that the DMD acts as a diffractive element – this becomes especially prominent in the infrared (IR) spectral region. The light diffraction causes serious spectral inhomogeneities in the light collection. We studied the effect of light diffraction via whiskbroom hyperspectral camera. Based on the knowledge, we designed a variety of different approaches to light collection, which use a combination lenses, off-axis parabolic mirrors, diffuser, light concentrator, and integrating spheres. By using an identical optical setup we mapped the efficiency and spectral homogeneity of each of the approaches. The selected benchmark was the ability to collect the light into fiber spectrometers working in the visible and IR range (up to 2500 nm). As expected, we have found the integrating spheres to provide homogeneous light collection, which however suffers from a 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 (400-2500 nm) and to map photoluminescence (PL) decay via time-correlated single photon counting technique. This allowed us to create one-to-one maps of absorption and PL inhomogeneities in samples. We see such setup as an ideal tool to study properties of luminophores and the effect of inhomogeneities on the PL properties.
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