Image processing outside the visible spectrum

May 17, 2022
Wavelengths outside of visible light are more meaningful than the light spectrum perceivable by humans. SVS-Vistek offers new powerful SWIR and UV industrial cameras as well as polarization cameras.

The human eye can detect light with wavelengths of about 400 to 750 nanometers. For many years, industrial image processing systems focused almost exclusively on this visible range. Due to the increasing performance of sensors in the short wave infrared (SWIR) and ultraviolet (UV) ranges, the economical use of special cameras outside the visible spectrum is now also possible in applications predestined for this.

Inspection with SWIR cameras is already a proven technology in a wide range of industrial sectors. The new SWIR cameras from SVS-Vistek are able to cover the visible range for the human eye with a single sensor in addition to the SWIR range. The combined use of the visible and SWIR ranges makes it easier, for example, to detect contamination as well as rot or pressure marks on fruit or vegetables on the selection belt, to inspect silicon in the solar and electronics industries, or to identify invisible impurities, water or water vapor with other technologies. Requiring only a single sensor for the complete wavelength range from 400 nm - 1700 nm results in significantly lower costs and less complex inspection systems. 

With the SWIR cameras exo990, fxo990 and exo991, SVS-Vistek currently has three powerful models in its range. With a resolution of 0.3 MP or 1.3 MP, frame rates of 90 to 259 fps, a very compact sensor format with a diagonal of only 8.2 mm or 4.1 mm, excellent temperature management and modern interfaces such as GigE Vision and CoaXPress-12, a wide range of applications can be implemented. The camera delivers excellent image homogeneity across the entire spectrum from 400 to 1700 nm. The technical basis is Sony's SenSWIR sensors, which are currently unrivaled on the market in this quality. A significant improvement compared to previous SWIR sensors is the so-called Cu-Cu bonding, which enables smaller pixel structures and thus improved resolution. State-of-the-art InGaAs technology, high resolution and sensitivity over a wide spectral range are the basis for the industrial SWIR cameras from SVS-Vistek.

New at the short end of the spectrum

The use of ultraviolet wavelengths, which lie in the spectrum from approximately 200 to 400 nm, has been less popular in industrial inspection than the use of SWIR-based cameras due to the low resolution of previously available UV cameras. With the new fxo487MCX and fxo487MXGE UV cameras, SVS-Vistek is fundamentally changing this situation. The 8.1 MP Sony sensor integrated into these cameras enables the detection of invisible product defects through ultra-sharp, high-resolution UV images. The most important areas of application for these cameras equipped with CoaXPress-12 or 10GigE interface are complex inspection tasks, e.g. in the battery, semiconductor, glass, recycling, gemstone and automotive industries. 

Cameras polarizing

Another interesting field for industrial inspection is polarization cameras. Here, too, a sensor development by Sony provides the basis for this innovative technology. The polarized sensors IMX264MZR, IMX250MZR and IMX253MZR work with a matrix of polarizing filters of different orientation (0°, 90°, 45° and 135°), which is applied directly on the sensor in each 2x2 pixel array. This setup has the advantage that with a single acquisition - without changing the illumination - the degree of polarization of the light, its polarization direction and the intensity of the polarized light can be measured and evaluated simultaneously. The simultaneous detection of different polarization directions and degrees enables reliable image evaluation on an optical basis. Changes to the mechanical or optical settings on the lens or the illumination are not necessary, which simplifies many tasks in image processing.

Based on these innovative sensors, SVS-Vistek currently offers six Polarized models of the EXO series with 5 or 12 megapixel resolution and frame rates from 10 to 75 fps. When it comes to the interfaces, users can choose between Gigabit Ethernet and USB3. With these polarized cameras, SVS-Vistek opens up interesting new possibilities compared to conventional industrial cameras. Polarization measurement allows, for example, non-metallic transparent or reflective materials such as water, plastic or glass to be inspected, as well as the inspection of difficult surfaces or the reading of black lettering on a black background, which was previously an almost impossible task in tire production, among other things. In the pharmaceutical industry, polarization cameras are particularly suitable for blister inspection in order to reliably detect and sort out defective tablet packaging or assemblies.

With a wide range of SWIR, UV and Polarized cameras as well as optimally matched illumination and optical components, SVS-Vistek is once again demonstrating its technical expertise in industrial image processing, even outside the visible light spectrum and will be happy to advise users on selecting the optimal combination for the task in hand.

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Courtesy of CMICRO Corp
Courtesy of New Imaging Technologies (NIT)
Courtesy of New Imaging Technologies (NIT)
Courtesy of New Imaging Technologies (NIT)
Courtesy of New Imaging Technologies (NIT)