DOI: 10.5061/dryad.n02v6wx17
title: Active and low-cost hyperspectral imaging for spectral analysis in low lighting environment

description: Hyperspectral imaging can capture information beyond conventional RGB
 cameras; thus, it has many applications, such as material identification
 and spectral analysis. However, like many camera systems, most of the
 existing hyperspectral cameras are still passive imaging systems: they
 require external light sources to illuminate the objects to capture the
 spectral intensity. As a result, the collected images highly depend on the
 environment lighting, and the imaging system cannot function in a dark or
 low-lighting environment. This work develops a prototype system for active
 hyperspectral imaging, which actively emits different single-wavelength
 lights at different frequencies when imaging. This concept has several
 advantages: first, using the controlled lighting, the magnitude of the
 individual bands is normalized to extract reflectance information; second,
 the system is capable of collecting information at the desired spectral
 range by tailoring the light sources; third, an active system is
 mechanically easier to make, since it does not require complex band
 filters as used in passive systems; last, such a system may work under low
 light or dark environments, which greatly facilitate
 underground/subsurface sensing applications such as borehole based mining
 exploration. This prototype is achieved by using an array of low-cost and
 single-wavelength LED (Light Emitting Diode) lights, a remote control
 module controlling the LED illuminator, and the shutter of a full spectrum
 camera. We demonstrate that such design is feasible and could yield
 informative hyperspectral images for spectral analysis and machine
 learning-based object identification in low light or dark environments,
 having great potential to benefit both the academic and industry such as
 in geochemistry, earth science, subsurface energy, and mining.
description: While capturing a hyperspectral image of an object, the system
 will loop over all 19 channels of LED lights and capture a panchromatic
 image for each of them. The illuminator consists of
 totaling four concentric circle rings. Each ring consists of 19 LED lights
 and has the same LED light bulbs to form a cluster that emits light at the
 same wavelength. The four LED lights for each cluster are placed at a 90
 interval to create sufficiently strong illumination, at the same time as
 distributed as possible to reduce the creation of shadows by direct
 lighting. The illuminator can illuminate lights at 19 unique wavelengths,
 and its actual implementation was achieved through planting these LED
 lights onto a circular PCB (Printed Circuit Board), powered by a 3W DC
 supplier and controlled through electrical switches. Each LED bulb has a
 dimension of 3.45mm x 3.45mm, driven by a direct current power
 supply. The selection of these 19 individual LEDs aims
 to cover the spectrum ranges as wide as possible. To this end, these 19
 monochromatic LEDs cover a spectral range of (365nm–1050nm), expendable
 depending on the spectral resolution of the lights and the wavelength they
 cover, which, for example, can be extended to the ultraviolet range (1400
 nm). It should be noted that most previous works use RGB LED mixers, which
 essentially mix the lighting spectrums of three single and fixed dye
 diodes that do not cover a spectrum beyond the visible range. In contrast,
 we directly use a single dye Diode that responds to a single electrical
 current excitement, which can directly emit lights at a narrow wavelength
 bandwidth at a higher spectral purity and operate beyond visible
 bands.
description: These hyperspectral images may use any image viewer to open.