Whereas multispectral imaging acquires the data in a discrete set of bands (typically, from three to ten), hyperspectral imaging (HSI) records the continuous light spectrum at each point of a scene. HSI is thus a powerful spectroscopy technique, measuring vast information that is then processed by numerical methods and AI algorithms to extract meaningful properties of the sample. Different technologies are available for HSI. Snapshot and tunable filter imaging cameras use bandpass filters, either on the pixel-level or using a filter wheel in front of a monochrome sensor. This guarantees fast measurements, at the expense of a limited number of bands. Push-broom cameras combine a dispersive spectrometer with a line scanning approach, making them suitable for in-line quality control. On the contrary, in applications where the samples are static, the need of adding a translation stage might result in a complex and impractical solution.
What’s new at this HSI camera?
Nireos novel HSI camera Hera has been specifically developed to target all the applications where the samples are static, combining great spatial and spectral resolution with high light throughput, ease of use and versatility. The camera is based on a Fourier-transform (FT) approach, coupling a monochrome sensor with a compact and robust interferometer. In this method, the interferometer splits the light into two temporally delayed replicas, whose interference pattern, measured by the sensor, provides the continuous spectrum. FT spectroscopy offers several well-known advantages over dispersive techniques: simultaneous wavelength measurement, higher throughput (not requiring any entrance slit or diffraction grating), precise wavelength accuracy, and adjustable spectral resolution without affecting the light throughput. Spatial resolution can also be adjusted independently. Given these advantages, this technique is often referred to as Ultraspectral Imaging. The Hera cameras are available in different models: VNIR (400-1,000nm), SWIR (900-1,700nm), eSWIR (1,200-2,200nm) and VIS-SWIR (400-1,700nm, see the next paragraph). They all feature a unique point&shoot approach: similarly to traditional cameras, the user can see the live monochrome image of the entire scene and adjust the focus, the iris aperture and the pointing direction before starting the measurement.
Brand new 400-1,700nm HSI camera
Hyperia is a novel HSI camera developed by Nireos, featuring an unprecedented 400-1,700nm spectral coverage, captured in a single measurement by using a single sensor. The camera has been developed with the contribution of the European Innovation Council (EIC) Transition program, GA 101058039 (www.hyperia-project.eu).
Applications
Given the operation modality and the specifications, the Hera cameras are versatile, and are employed in many remote sensing applications, including food, vegetation studies, and cultural heritage. Notably, the cameras can also be easily connected to any commercial microscope (Fig. 1c) to obtain hyperspectral images with sub-micrometric resolution, either in transmission, reflectance, or fluorescence, with applications ranging from microbiology to material science. Fig. 1a and 1b show the segmented hyperspectral image of two mouse lung tissues, respectively healthy and fibrotic, the difference being the spatial distribution of the elastin (green) and the red blood cells (purple), which are characterized by the fluorescence spectra shown in Fig. 1d. In the semiconductor industry, the camera is widely employed to characterize defects or inhomogeneities of the materials, typically via their emitted electroluminescence signal, and to measure the thickness of the different layers deposited on top of silicon wafers (Fig. 2). Figure 2b shows the inhomogeneous thickness distribution, which can be retrieved by measuring the spectral fringes shown in Fig. 1c. This information is of paramount importance in quality control procedures in the semiconductor industry.