Three-dimensional hyperspetral camera based on near-infrared single-pixel imaging

This work presents the development of a multi-spectral vision system that combines different technologies detecting radiation in the visible spectrum (380-750 nm wavelengths), in the near-infrared NIR (1550 nm wavelengths), in the thermal spectrum band 1.4µm, and 77 GHz millimeter band. The main motivation of the this work is to propose a new hyperspectral approach to overcome the limitations present in commercial vision systems, such as the high amount of memory needed to generate images, the low quantum efficiency of silicon sensors, noise due to disturbance of the visible spectrum, limitations caused by foggy or low visibility conditions, and the difficulty to determine the depth information for objects in the image. Therefore, we propose a hybrid vision system that combines the capabilities offered by RADAR technology at the a range of tens or hundreds of meters, the ability to trace surfaces and operate under low visibility conditions, using a vision system based on single-pixel imaging (SPI) operating in the near-infrared NIR (@ 1550 nm) part of the spectra and Time-of-flight (ToF) based system using an InGaAs high quantum efficiency detector (QE(λ)>80 @ 1550 nm wavelength). Furthermore, SPI systems have a high intrinsic compression capacity at the hardware level, so less memory is needed for image generation, reaching PSNR values > 20 db (the PSNR level acceptable image quality in the industry is between 20 and 50 dB). Developing a system with these characteristics offers a high advantage for applications such as drones, autonomous vehicles, and other techniques that operate with 2D/3D vision or video systems. For the implementation of the system, a structured lighting SPI architecture was developed using an array of 32 x 32 NIR LEDs emitting radiation in the wavelength of 1550 nm that operates in combination with other technologies such as an 80 GHz millimeter band radar, a Time-of-flight system based on four pulsed lasers, a 32 x 24 thermal camera sensor, and a camera with northern vision capability. The developed vision system has an operating range of 37.5 mm to 5 m with a maximum spatial resolution of 10 mm in the distance range below 1 m. As a single-pixel image processing strategy, the Orthogonal Matching Pursuit (OMP) compressed sensing algorithm supported on a GPU architecture is used to achieve a processing times of below 30 ms, which corresponds to a 24 frame/sec video rate.

Future applications NIR-SPI hyperspectral system

The last decade has promoted different detection technologies adapted to different conditions in rainy, fog, or low-visible scenarios. The object detection under scattering conditions has converter in a challenge to which they have proposed some solution as use of the RADAR or LIDAR . A point important to considerer in a scattering condition is the elastic Mie scattering effects which in NIR spectrum decreases, for which a NIR-SPI system is a solution efficiency with low-cost and integration which in recent years have improved, reaching processing times close to real-time and capacity of 3D images. Therefore, these offer an advantage for its integration in systems perception using today in different vehicles, where it doesn't need to have a high-quality image for application as vision sensors detect and avoid obstacles, 2D/3D pre-mapping, or navigation applications.

Our NIR-SPI system developed if adopted in UAVs (see Fig. 1) offers a solution to perform better visualization of the scene in outdoor conditions. If compared to conventional vision systems that usually use RGB sensors operating in the visible spectrum. As explained, conventional systems operating in the VIS range present much higher image degradation in scattering conditions than those operating in the NIR part of the spectra. The integration of our NIR-SPI system into UAVs increases spectral capacity detection. In addition, it provides fast deployment at remote or challenging locations, being essential for many civil and military applications such as post-disaster relief assistance. Therefore, we believe that the NIR-SPI system presented has a great potential to be used in similar applications. Furthermore, SPI could be an alternative to the use of LIDAR technology.

Fig. 1. Future applications NIR-SPI hyperspectral system recues Drone

SPI applications are not limited to vision sensors, but new applications have also been developed. For example, in VR/AR systems, we can cite MEMSEye system that works using SPI and MEMS mirror to a generation of 3D images (see Fig .2b), and applications in holography . Others applications that are studied is adaption as vision system for ROVs or underwater, SPI-RADAR (see Fig.2c), and hyper-spectral . This later field of application has great importance in the area medical [241] (see Fig. 2d), the space exploration , and CubeSat.

Fig.2. Overview of new fields for applications system vision SPI: (a) SPI-LIDAR , (b) VR/AR , (c) SPI-RADAR , (d) SPI-medical.