A new approach for near-infrared (NIR) hyperspectral imaging collects both spectral and spatial information to create detailed 3D datasets. Published in Nature’s Light | Science & Applications imprint, the method uses self-assembled colloidal quantum dot (CQD) color filters with tunable absorption properties and a digital micromirror device (DMD) to encode spectral and spatial data. The research focus of a team at Shandong University, the novel single-pixel detector then captures this information, offering a potentially simpler and more affordable alternative to traditional hyperspectral systems that rely on costly large, two-dimensional detector arrays.

Hyperspectral imaging aims to obtain a spectrum for each pixel in an image, enabling the identification of objects and materials based on their spectral signatures. The near-infrared (NIR) region of the electromagnetic spectrum, spanning wavelengths from 780 nm to 2500 nm, is particularly useful for a range of applications including medical diagnostics, agriculture, and defense. Yet current NIR hyperspectral imaging systems face limitations in terms of cost and complexity.

Toward greater NIR hyperspectral imaging accessibility

Central to this novel system developed at Shandong University are CQD, which offer several advantages over conventional edge-pass or band-pass filters for spectral encoding. The researchers highlight that owing to “the randomness and variability present in the absorption spectra of CQDs, CQD filters facilitate precise modulation of target spectra across various wavelengths.” This capability translates to finer spectral resolution and improved reconstruction accuracy compared to binary encoding methods. In addition, the tunability of CQD absorption properties through size control further adds to their versatility and potential for miniaturization.

In an announcement, the researchers discuss on how their research can cut system complexity, noting:

“By combining a single-pixel detector with CQD filters, we eliminate the need for a costly 2D arrayed sensor typically employed in conventional hyperspectral imaging systems, thereby reducing system complexity and cost. The attained spectral reconstruction and spatial resolving capabilities showcase the effectiveness of our system and the promising potential for affordable and portable hyperspectral imaging devices.”

“Moreover, our strategy integrates both spectral and spatial encoding, potentially allowing for simultaneous and intertwined reconstruction of both spectra and images through the direct application of a compressed sensing algorithm on the hyperspectral data cube.”

Next steps

In the future, the researchers aims to further refine and expand the capabilities of CQD-enabled single-pixel NIR hyperspectral imaging. As the authors suggest in their article, the “flexible fabrication process of CQDs” and advances in optical field modulation techniques can support miniaturization of both the spectral and spatial modulation modules, “potentially leading to enhanced spectral and spatial resolution.” Additionally, the inherent affordability and portability of this approach “shows promise in advancing affordable and accessible NIR hyperspectral imaging technologies,” they write. Potential applications could span a number of fields such as agriculture, food safety, and medical diagnostics.

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