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Technology

Technology

FROM COLOR TO HYPERSPECTRAL IMAGING:
A BRIEF HISTORY

Spectroscopy originates from the study of visible light dispersed according to its wavelength. Widely used RGB color cameras capture three wavelength ranges (red, green, blue) of the visible region of light (400 – 750 nm). As color information is not sufficient for many applications, the industry demands possibilities to integrate highly sophisticated spectroscopy used in laboratories to analyze the invisible region of light in high speed applications.

Spectral technology

The biggest hurdle was the large dataset generated by processing the full spectrum of each pixel. As a first step, multispectral devices have been introduced to the market analyzing defined spectral bands.

Hyperspectral Imaging (HSI) technology provides for each local point of the line scan a complete spectrum with high resolution in parallel. HSI technology of EVK is using an imaging spectrograph in combination with an area sensor. This system has no moving parts and is able to scan a line with high local and spectral resolution.

Spectograph technology

This technique is known as push-broom scan and results in a so-called HSI data cube. It is well suited to record a material stream on conveyor belt or chute, for example.

HSI Data Cube

The HSI data cube represents the 4 recorded dimensions:

The scanned line is represented on the x-axis. The corresponding spectral information of each pixel is displayed on the z-axis. The time axis charts the subsequent line-scans of the moving direction. For the fourth dimension, the intensity of the reflected light per spectral pixel is stated color coded with artificial color representation.

EVK was the first company that succeeded in building a compact line scanner in hyperspectral imaging technology with a data processing unit integrated in the camera system. HELIOS, the hyperspectral smart camera system, measures in parallel the absorption spectrum of each illuminated pixel in a line according to the molecular structure.

The intensity of the reflected light per wavelength is represented in each spectrum and describes the chemical properties of an object like a fingerprint.

The intensity of the reflected light per wavelength is represented in each spectrum and describes the chemical properties of an object like a fingerprint.

Because the entire spectrum is acquired for each pixel, this is the best technology for many different applications. For C-O-H-N combinations, the major analytical bands and their relative peak positions are well known. This simplifies the adaptation of the system to new tasks. The processing of these spectra with multivariate data analysis allows a qualitative or quantitative differentiation per pixel.

Chemical Imaging Technology (CIT) pictures the invisible chemical properties of an object:

Color Chemical technology

The colors on the screen correlate with the molecular information of every pixel of the image. Relevant color visualization of different spectra is realized by the sophisticated EVK proprietary classification system, which is an integral part of the HELIOS hyperspectral camera.

The chemical object properties are assigned to RGB color channels. Different colors can be assigned to related molecular structures to simplify interpretation.

Invisible chemical properties are now visible.

Chemical Imaging Technology (CIT) gives a boost to totally new tasks and improves the detection of foreign bodies and impurities with minimum spectral deviation. The result is an analyzing or sorting process with the highest quality.