Hyperspectral imaging (HSI) is a cutting-edge technique that captures and processes information across the electromagnetic spectrum. Unlike traditional imaging methods that capture light intensity at specific wavelengths, HSI collects a full spectrum at each pixel in an image, allowing for the differentiation of materials based on their unique spectral signatures. Near-infrared hyperspectral imaging (NIR-HSI) has gained attention in the food and industrial sectors as a non-destructive method for analyzing object composition. One significant aspect of NIR-HSI is over-thousand-nanometer (OTN) spectroscopy, which can identify organic substances, estimate concentrations, and create 2D maps. Moreover, NIR-HSI can provide deep insights into the body by visualizing lesions hidden within normal tissues.
A variety of HSI devices have been developed for different imaging targets and situations, including microscopy, portable imaging, and confined spaces. However, for OTN wavelengths, conventional visible cameras lose sensitivity, and few lenses are available to correct chromatic aberration. Furthermore, constructing cameras, optical systems, and illumination systems for portable NIR-HSI devices requires the integration of a rigid scope, which has not been achieved yet. In a recent study, a team of researchers from Tokyo University of Science and other institutions developed the world’s first rigid endoscope system capable of HSI from visible to OTN wavelengths, which was published in Optics Express.
The new system features a supercontinuum (SC) light source and an acoustic-opto tunable filter (AOTF) that can emit specific wavelengths. This combination allows for easy light transmission to the light guide and the electrical switching between a broad range of wavelengths. The researchers verified the system’s optical performance and classification ability, demonstrating its ability to perform HSI in the range of 490-1600 nm, enabling visible and NIR-HSI. The system showed advantages such as low light power and downsizing capability, along with a more continuous NIR spectrum compared to conventional devices.
To showcase the system’s capability, the researchers acquired spectra of six types of resins and utilized a neural network to classify the spectra pixel-by-pixel in multiple wavelengths. The results showed high accuracy in classifying different targets, including resins and a white reference, with reproducibility and specificity. Future research directions for improving this method include enhancing image quality and recall in the visible region and refining the rigid endoscope design to correct chromatic aberrations. The proposed HSI technology is poised to revolutionize industrial inspection and quality control, offering a “superhuman vision” tool for new ways of perceiving and understanding the world.
The integration of expertise from various fields through a collaborative, cross-disciplinary approach in this breakthrough enables the identification of cancer areas and the visualization of deep tissues during medical procedures, leading to improved surgical navigation. The technology also allows for measurements using previously unseen light in industrial applications, potentially opening up new areas for non-destructive testing. By visualizing the invisible, the researchers aim to accelerate medical development and enhance the quality of life for both physicians and patients.
