SILIOS Multispectral Cameras for Video Rate Spectral Imaging
Pro-Lite is delighted to announce that it is now a distributor for the multispectral cameras made by SILIOS Technologies (Peynier, France). In the field of spectral imaging, what multispectral cameras concede to hyperspectral imagers in spectral resolution, they gain in terms of speed and relative affordability. The SILIOS technical approach creates spectral imagers that operate in near real-time, making them perfect for capturing fast-moving objects at video frame rates.
Spectral Imaging
The term “spectral imaging” has been adopted to describe cameras which can analyse the spectrum of reflected or emitted light. Let’s first consider how a colour camera works. An RGB colour camera typically employs a Bayer pattern of red, green and blue bandpass filters applied directly onto the image sensor to form a colour image. Simplistically, you can regard one third of the sensor’s pixels as filtered green, one third blue and one third red. Software interpolation of the separate RGB pixels is used to recreate a full frame colour image. The spectral information contained in a colour image is limited to the amount of visible light which passes through the bandpass RGB filters. In other words, this is not spectral data per se, rather an image which correlates to some extent with the colour of the object that we would perceive.
An RGB colour camera represents a spectral imager in its simplest form, using three spectral bands for collecting light in the red, green and blue wavelength regions. However, most spectral cameras can resolve within more than three bands, and with a greater number of bands, spectral imaging can yield much richer spectral data.
Multispectral Versus Hyperspectral Imaging
Spectral imaging cameras can be loosely defined as being either multispectral or hyperspectral devices. The distinction is often based on the number of wavebands detected by a camera.
- Multispectral cameras capture images in a limited number of discrete spectral bands, typically between 3 and 10. Each band represents a broad section of the spectrum (some tens of nanometers), making multispectral imaging suitable for applications requiring general spectral insights. A multispectral image produces a smaller datafile which allows for faster processing and real-time analysis.
- Hyperspectral cameras acquire data across hundreds of contiguous, narrow spectral bands. This provides finer spectral details for precise material differentiation but requires significant computational power and storage due to the vast amount of data collected.
Generally, multispectral imagers do not reproduce the reflected spectrum of an object but measure at multiple discrete wavebands instead. This approach reveals information beyond what standard imaging techniques can provide, making multispectral imaging an invaluable tool in numerous industries, including agriculture, environmental monitoring, medical diagnostics, and industrial quality control. By analysing how objects reflect or emit light at different wavelengths, multispectral imaging enables precise material identification, quality assessment, and scientific exploration.
The SILIOS COLOR SHADES® Mosaic (CSM) Filter Technology
SILIOS Technologies implements its proprietary COLOR SHADES® Mosaic (CSM) filter technology in its multispectral cameras. This innovative approach involves integrating a mosaic of spectral filters directly onto the camera sensor, allowing each pixel to capture specific spectral information (Figure 2). The CSM filter technology offers several advantages over competing technologies.
- Compact and lightweight design. Since the spectral filters are directly applied to the image sensor, no additional optical components are needed, reducing size and weight.
- Simultaneous multispectral imaging. Unlike traditional systems that rely on filter wheels or sequential capture, CSM technology enables real-time, video-rate, “snapshot” spectral imaging across all bands in a single exposure.
- Enhanced accuracy and stability. The fixed filter configuration ensures consistent spectral performance, reducing errors introduced by moving parts.
- Cost efficiency. By integrating spectral filtering at the sensor level, SILIOS cameras provide a high-performance, cost-effective solution for multispectral imaging applications.
This technology is implemented across all SILIOS cameras, enhancing their ability to capture precise spectral data whilst maintaining a compact form factor and high efficiency.
The COLOR SHADES® technology is a unique manufacturing technique for the realisation of multispectral pixelated filters. The filters are composed of several cells, each of which is filtering a given wavelength band. The number of cells, their size, geometry and layout onto the filter, the number of bands and their centre wavelengths are all configurable.
The main advantages of COLOR SHADES® technology are the flexibility in the filters and cells sizing, the flexibility in the choice of the wavelength centering, and the reduced filter cost thanks to the use of collective manufacturing methods.
Consider the SILIOS CMS V1 multispectral camera (Figure 3). This employs a CMOS sensor with 1280 x 1024 pixels (1.3MP) with 8 spectral subchannels centred on 590, 630, 670, 710, 750, 790, 830 and 850nm. Each set of 9 camera pixels with these filters applied forms a “macro-pixel” (one pixel is left without a filter applied, for black & white imaging).
Overview of the SILIOS Range of Multispectral Cameras
SILIOS Technologies offers a range of “off-the-shelf” multispectral cameras for the VIS, NIR and SWIR wavelength ranges. The CMS series VIS/NIR cameras are based on COLOR-SHADES® pixelated filter technology, combined with either 1.3MP or 4.2MP CMOS sensors for the 400-900nm band. For the near infrared band, a 1.3MP InGaAs sensor addresses the 1100-1600nm wavelength range.
SILIOS CMS Series Cameras
These compact and lightweight cameras use a 1.3 Megapixel CMOS sensor and capture images across 8 spectral bands plus one black-and-white reference channel. Variants include:
- CMS-C for visible spectrum applications, 430–700nm.
- CMS-V covering visible to near-infrared wavelengths, 550–830nm.
- CMS-S for near-infrared applications, 650–930nm.
The CMS Series is widely used in colour measurement, industrial process control, and in vegetation analysis.
SILIOS CMS4 Series Cameras
Derived from the CMS 1.3MP series, the CSM4 feature a higher-resolution 4.2 Megapixel CMOS sensor. They retain the same 8-band spectral configuration and provided improved spatial resolution. CMS4 cameras are well-suited for applications requiring detailed image capture without sacrificing spectral accuracy.
SILIOS TOUCAN Camera
The TOUCAN is a broadband snapshot multispectral camera that captures 4.2 Megapixel raw images on a CMOS sensor, made up of ten 512 x 512 pixel spectral sub-images covering the complete spectral range from 400-900nm in one camera (Figure 4). The resolution of the TOUCAN (the ability to discern adjacent wavelengths) is 30-50nm. It is ideal for applications demanding comprehensive spectral analysis, such as precision agriculture, environmental research, and medical diagnostics.
SILIOS CICADA Camera
The CICADA is a SWIR camera that operates within the 1100–1700nm range using a 1.3 Megapixel InGaAs sensor (Figure 5). Its high sensitivity in the SWIR band combined with its high spatial resolution make it ideal for material sorting, pharmaceutical inspection, and mineral exploration.
Applications of SILIOS Multispectral Cameras
Spectral imaging is a recent and developing science, and more and more applications are being addressed by multispectral cameras that can detect and classify objects based upon more than just their visible colour and reflectance. Some of the more common applications can be found in agriculture, environmental science, earth observation and remote sensing, defence, cultural heritage and in healthcare.
Precision Agriculture
Multispectral cameras help monitor crop health, detect stress factors, and optimise irrigation and fertilisation strategies. By analysing spectral data, farmers can identify issues such as nutrient deficiencies, disease outbreaks, and water shortages.
Environmental Monitoring
Multispectral imaging enables the assessment of vegetation changes, water quality, and land use alterations. This technology is essential for conservation efforts and ecological research.
Industrial Quality Control
Multispectral cameras enhance non-destructive inspection in manufacturing processes by detecting defects, ensuring colour consistency, and verifying material composition.
Medical Diagnostics
Healthcare professionals use multispectral imaging for tissue characterisation, wound assessment, and the detection of conditions that are difficult to observe with conventional imaging.
Remote Sensing
Multispectral cameras are used in earth observation and remote sensing, to provide vital data for mapping, urban planning, and natural resource management.
Security & Defence
In the defence field, multispectral cameras can penetrate smoke and camouflage.
Artworks & Cultural Heritage
Multispectral cameras are employed in cultural heritage to help analyse and preserve artworks by revealing hidden layers, previous restorations as well as any underdrawings.
In Conclusion
By offering a diverse range of multispectral cameras, SILIOS Technologies provides high-performance solutions tailored to the needs of industries requiring advanced spectral imaging capabilities.
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