ULTRIS X20 vs. ULTRIS S5 vs. FireflEYE V185
When the FireflEYE V185 was launched in 2012, it was the first hyperspectral camera capable of acquiring a complete hyperspectral data cube (x, y, λ) with a single image shot. The prism-based sensor technology provided a light efficiency of up to 70%. With 125 spectral channels (450 nm to 950 nm) and an image size of 50×50 pixels, the camera could simultaneously record 2,500 spectra. However, with only 50×50 pixels, resolving spatial structures in the image was challenging. To address this, a second sensor with a single band (panchromatic) was integrated into the camera, capturing the same view at a higher resolution of 1000×1000 pixels. This allowed users to perform pansharpening on the spectral data, transforming the final data cubes to a maximum size of 1000 x 1000 x 125.
Today, the new Cubert ULTRIS cameras break new ground as the first HSI cameras based on light field technology. The ULTRIS X20 features an Ultra-HD CMOS sensor with 20 MP, making it the highest-resolution imaging spectrometer worldwide at its release in 2021. During image acquisition, the object is captured with multiple images, each with its own optical bandpass filter at different center wavelengths.
Depending on the ULTRIS camera model, this is achieved by combining a lenslet array with a mosaic bandpass filter (ULTRIS X20) or a continuously variable bandpass filter (ULTRIS S5). The ULTRIS X20 provides a native image resolution of 410 × 410 pixels with 164 spectral channels, continuously covering the wavelength range from 350 nm to 1000 nm, producing an unprecedented 168,000 spectra per image, acquired simultaneously. The ULTRIS S5 offers a native image resolution of 290 x 275 pixels with 51 channels, covering the range between 450 nm and 850 nm. The cameras’ 12-bit sensors allow for detecting minute intensity differences in the spectral content while maintaining a low noise level. The GigE camera interface ensures an image frame rate (depending on the model) of up to 8 Hz and 15 Hz, respectively.
In a comparative test, the three cameras (FireflEYE V185, ULTRIS X20, ULTRIS S5) were installed in the same setup for image comparison. The exposure time was optimized using a white reference to derive the maximum dynamics. A stabilized tungsten light source (100 W) was used for illumination, with exposure times of 12 ms (FireflEYE V185), 3 ms (ULTRIS X20), and 47 ms (ULTRIS S5). The reflectance properties of the test samples were calculated by subtracting the dark current image from the measurement image and subsequently dividing it by the image of a calibrated 95% white reference (Zenith Lite). The dark current measurement and the white reference were averaged 20 times to achieve good noise reduction.
However, the measurements were acquired without averaging or post-processing to allow a direct comparison of the data. The images are presented in their original form without sharpening or smoothing the spectral information to show the true spectral quality of each sensor.
The image comparison chart above shows quantities derived from the hyperspectral data cubes. The first and second rows display typical RGB (True color) and CIR (Color infrared) images. The bottom row shows a typical index used for vegetation analysis. Each pixel in the different images represents one spectral curve from the respective sensors.
For the FireflEYE V185, the low spatial resolution is evident. On the other hand, the color representation is very clear, which is confirmed by the noise-free images of the vegetation index. The ULTRIS S5, while having lower spatial resolution and fewer channels, offers similar spectral quality, small size, and weight. Additionally, the camera is specifically designed for industrial applications. The ULTRIS X20 combines high spatial resolution with low color variation (low standard deviation). Both the image and spectral quality are excellent, with image noise comparable to the FireflEYE V185.
Spectral Quality Comparison
The comparison of the spectral quality of the three hyperspectral imaging cameras (FireflEYE V185, ULTRIS S5, ULTRIS X20) shows the spectra of red, green, and yellow samples, along with the respective noise-indicating standard deviation. The graphs illustrate the spectral signature of three differently colored paper samples for each camera. The spectra of all pixels in a predefined area with homogeneous color were averaged. The standard deviation, representing the noise equivalent of the sensors, is used as error bars for each channel.
Conclusion
In general, it is possible to measure in the ultraviolet range (UV) with the ULTRIS X20, which can provide additional relevant information for specific applications. However, for this comparison, only a halogen light source was used, so the UV range is grayed out in the ULTRIS X20 plot.
The results clearly demonstrate that the ULTRIS X20 can easily match the spectral quality of the FireflEYE V185, even though the ULTRIS X20 offers a significantly higher spatial resolution.
About the Author
Dr. Viktoriya Tsyganskaya is the Head of Project Management at Cubert GmbH and has been leading research and customer projects since 2018. She earned her PhD in Remote Sensing from Ludwig Maximilian University of Munich, specializing in radar remote sensing and environmental monitoring. Viktoriya has extensive experience from her scientific work, including the project “Dikes under Pressure,” and expertise in sustainable environmental solutions. Her deep knowledge in remote sensing makes her a key contact for innovative hyperspectral technologies at Cubert.
