Hyperspectral Imaging

See what’s invisible to the naked eye

With hyperspectral imaging, you can analyze and sort any material: See what’s under the skin of an apple, detect fungicides, or analyze the composition of fish or meat. In short, get a fingerprint of your sample.

For this, you need a bright, stable, and focused light source to make reliable, repeatable measurements. Compared to incandescent lamps, a SuperK laser has many advantages.

Incandescent lamps develop heat. They have a short lifetime and poor brightness. A SuperK laser delivers focused light and offers better thermal management. It has a long lifetime and a high brightness which give you a high resolution and a short sampling time.

Get enough light

Hyperspectral imaging is an emerging imaging technique in many applications, from food and recycling sorting to medical imaging and semiconductor metrology. It can help you sort materials based on multiple spectral features. The image is made by recording individual pixels per nanometer and reconstructing them into a hyperspectral image.

In many applications, ambient light or incandescent lamps will not provide enough light. For high-performance systems, you need advanced light sources such as the SuperK lasers. Compared to other light sources, SuperK offers a higher resolution and better signal-to-noise ratio resulting in higher throughput.

Get additional information from the SWIR spectrum

When talking about hyperspectral imaging, we must mention the short-wave infrared spectrum, SWIR. Using light in the 1700 – 2500 nm spectrum lets you see things that are invisible when using other wavelengths. This is relevant, e.g., for the sorting of minerals.

It is difficult to find appropriate light sources that cover the SWIR spectrum. LEDs and incandescent light bulbs do not cover these wavelengths, and halogen lamps have limited power in the SWIR range. Conventional lasers can give light at discrete wavelengths, but only a supercontinuum laser, such as the SuperK laser, offers light in the 1700 – 2500 nm spectrum.

A SuperK laser gives you single-mode light that can be focused into a small spot or a narrow line and still keep its high brightness.

Analyze and sort anything 

A hyperspectral imaging set-up lets you analyze and sort anything. You can sort general waste and different plastic types, classify textiles, determine mineral composition, detect food adulteration, and much more…

Food sorting is getting a lot of attention at the moment. If you work with meats, produce, or processed foods, a hyperspectral imaging set-up lets you look for, e.g., bruising, ripening, pesticide residues, skin defects, internal defects, sugar content, protein, fungicide, fat, salt, moisture, blood, bones, freshness, and meat structure.

Different sorting techniques see different things

Scan types

In the production line, you can use different sorting techniques:

• Point scan
• Line scan (or push broom)
• Wavelength scan
• Snapshot imaging

Laser light can be tightly focused, so the SuperK laser is especially well-suited for point scan, where you need a small light spot, and line scan, where you need a narrow line of light.

Reflectance, transmittance, or scattering

When you work with point or line scanning you can apply three sorting techniques, depending on what you want to see.

• Reflectance-based measurements are employed to study the surface properties of the samples.
• Transmission-based measurements are employed to study the properties of the bulk of the materials deeper within the samples.
• Trans-interactance measurements are typically used to study the light interaction of the materials in a shallow volume of samples. This scattering measurement method is less sensitive to the surface properties of the sample.

Our SuperK laser can be used as the light source for hyperspectral imaging in chute feeds, conveyor belts, or channels.

A wide and stable spectrum

To make reliable, repeatable measurements, your light source must have high brightness and a broad, flat, and stable spectrum.

Unlike, e.g., LEDs, SuperK lasers have no wavelength peaks, and because the spectrum is flat compared to lamps, the signal-to-noise ratio is easy to manage. The SuperK covers the visible, nIR, and SWIR wavelengths from 400 – 2500 nm.

Ultimate brightness

With a SuperK, you can focus the perfectly collimated output beam without losing intensity. Its light is 100 times brighter than any comparative incoherent light source.

You get more signal – even when measuring diffuse, opaque, and scattering materials. The high brightness gives you a high sorting speed.

Install and forget!

At the heart of the SuperK, you will find our renowned Photonic Crystal Fiber (PCF) technology. This solid-state, all-fiber architecture ensures a reliable 24/7 operation and runs maintenance-free for 10,000 hours – the longest in the market.

Intended for industrial use, the SuperK is easy to mount and handle due to its rugged and compact design. Reliability, quality, and performance are ensured through the DIN ISO 9000 certified processes.

Light sources pros & cons

All light sources have pros and cons. Let’s sum them up.

Read the application note if you want to know how to use a SuperK EVO for hyperspectral imaging.

Plastic sorting setup from Laser Munich 2022

Calibration makes sensors intelligent

The market for optical sensors is growing as we tend to put them into more of our everyday necessities and gadgets. But for optical sensors to work properly, they need – like any other measurement instrument – to be calibrated.

Calibration and clever processing add value to inexpensive sensors and transform them into power meters, chemical sensors, ambient light sensors, etc. The calibration process adds value to the sensor by defining it relative to other sensors.

Almost any calibration process consists of submitting a sensor to well-defined and traceable stimuli and recording the response. In most cases, many different stimuli must be recorded to get the full picture.

Most light sources have limitations

Color-sensitive optical sensors must be calibrated for a range of wavelengths. If a high spectral resolution or a high spatial resolution is needed, only a few sources are suitable. And if both are needed, even fewer sources can be used.

Laser arrays and LED arrays offer relatively high powers and especially lasers exhibit high brightness. But they lack spectral flexibility and continuous spectral coverage.

Incandescent lamps and most gas discharge lamps offer a broad and continuous spectral coverage but with poor brightness. The lack of brightness can be a challenge in applications where high spatial resolution is required for instance if there is a need to transmit the light far in free space with low loss to the device under test (e.g. inside a vacuum chamber). Furthermore, if filtering equipment requires a high spectral resolution, high brightness is an advantage.

Why is that? Many narrowband tunable optical filters and monochromators require a relatively high brightness input to work efficiently. An example could be a monochromator where high spectral resolution requires a small input slit, which causes a significant power loss for low brightness sources.

Bright and broad continuous light

This allows calibration instrument manufacturers to make rapidly tunable sources to map out the performance of the device under test as well as generate broadband standard illuminants for control purposes. These are features that make the supercontinuum source ideal for the calibration of optical components.

We offer customized and turnkey supercontinuum calibration solutions. All include fully integrated sources, filters, software, and delivery optics. They are based on a field-proven instrument architecture, industrial and scalable production, and backed by a worldwide support network.

Publications

• Hyperspectral reflectance measurements from UAS under intermittent clouds: Correcting irradiance measurements for sensor tilt by Christian J. Köppl, Radu Malureanu, Carsten Dam-Hansen, Sheng Wang, Hongxiao Jin, Stefano Barchiesi, Juan M. Serrano Sandí, Rafael Muñoz-Carpena, Mark Johnson, Ana M. Durán-Quesada, Peter Bauer-Gottwein, Ursula S. McKnight, Monica Garcia published in Remote Sensing of Environment, 2021.
• Characterization of Nancy Grace Roman Space Telescope slitless spectrometer (grism) by Qian Gong, Matthew Bergkoetter, Joshua Berrier, Victor J. Chambers, Margaret Dominguez, Wesley Fincher, John Hagopian, Catherine Marx, Laurie Seide published in Journal of Astronomical Telescopes, Instruments, and Systems, 2020.
• A Broadband Mid-Infrared Trace Gas Sensor Using Supercontinuum Light Source: Applications for Real-Time Quality Control for Fruit Storage by Khalil Eslami Jahromi, Qing Pan, Amir Khodabakhsh, Cor Sikkens, Paul Assman, Simona M. Cristescu, Peter M. Moselund, Maxime Janssens, Bert E. Verlinden, Frans J. M. Harren published in European Conference on Biomedical Optics proceedings, 2019.
• WFIRST Grism Characterization by Qian Gong, Matthew Bergkoetter, Joshua Berrier, John Chambers, Margaret Dominguez, Wesley Fincher, John Hagopian, Cathy Marx published on NASA Technical Reports Server, 2019.
• Flavinium Catalysed Photooxidation: Detection and Characterization of Elusive Peroxyflavinium Intermediates by Jan Zelenka, Prof. Dr. Radek Cibulka, Prof. Dr. Jana Roithová published in Angewandte Chemie, 2019.

References

• Spectrally resolved radiometric characterization and calibration using a supercontinuum laser in the NIR by L. Bünger, R.D. Taubert, and K. Anhalt for the AMA Conferences – Sensor 2015 and IRS² 2015, DOI 10.5162/irs2015/1.2.

Imagine the brightness of a laser with the spectrum of the sun!

Are you looking for a light source for solar cell characterizing? A bright and broad light source with high pointing stability and a single-mode profile?

You can get this and more from our SuperK supercontinuum white light lasers. They are ideal sunlight simulators.

High pointing stability is crucial when you direct light onto and perform measurements on tiny structures.

The single-mode beam profile lets you focus the light into tiny spot sizes as small as the structures you are characterizing.

Broadband and tunable

If you add a filter, you convert the SuperK laser into a tunable broadband light source. This way, you can simulate both the power and wavelength over a broad bandwidth and make absorption and transmission measurements on solar cells and other photovoltaic materials.

Our SuperK lasers give you bright diffraction-limited light from 390-2400 nm. Fiber delivered and collimated. You even get MHz picosecond pulses with tunable repetition rate and adjustable delay.

Our industrial white light lasers typically run 24/7 for more than a full year without any service.

Publications

• Optimizing the Photovoltaic Performance of Organic Solar Cells for Indoor Light Harvesting by Mengmeng Cui, Prof. Aifeng Lv, Prof. Zaifei Ma published in ChemPhysChem, 2022.
• Wide-bandgap organic solar cells with a novel perylene-based non-fullerene acceptor enabling open-circuit voltages beyond 1.4 V by Jakob Hofinger, Stefan Weber, Felix Mayr, Anna Jodlbauer, Matiss Reinfelds, Thomas Rath, Gregor Trimmel, Markus C. Scharber published in Journal of Materials Chemistry A, 2022.
• Photoprotection in metal halide perovskites by ionic defect formation by Nga Phung, Alessandro Mattoni, Joel A. Smith, Dieter Skroblin, Hans Köbler, Leo Choubrac, Joachim Breternitz, Jinzhao Li, Thomas Unold, Susan Schorr, Christian Gollwitzer, Ivan G. Scheblykin, Eva L. Unger, Michael Saliba, Simone Meloni, Antonio Abate, Aboma Merdasa published in Joule, 2022.
• Fully Vacuum-Processed Perovskite Solar Cells on Pyramidal Microtextures by Lidón Gil-Escrig, Marcel Roß, Johannes Sutter, Amran Al-Ashouri, Christiane Becker, Steve Albrecht published in RRL Solar, 2021.
• Four-terminal perovskite/silicon tandem solar cell with integrated Mie-resonant spectral splitter metagrating by Verena Neder, Dong Zhang, Sjoerd Veenstra, Albert Polman, 2020.
• Humidity-robust scalable metal halide perovskite film deposition for photovoltaic applications by Carlo Andrea Riccardo Perini, Anil Reddy Pininti, Samuele Martani, Peter Topolovsek, Andrea Perego, Daniele Cortecchia, Annamaria Petrozza, Mario Caironi published in Journal of Materials Chemistry A, 2020.
• Sensitization of silicon by singlet exciton fission in tetracene by Tony C. Wu, Markus Einzinger, Julia Kompalla, Hannah Smith, Collin Perkinson, Leas Nienhaus, Sarah Wieghold, Daniel Congreve, Nicholas Thompson, Antoine Kahn, Moungi Bawendi, Marc A. Baldo published in  SPIE Nanoscience + Engineering proceedings, 2020.
• Dimensionally Engineered Perovskite Heterostructure for Photovoltaic and Optoelectronic Applications by Sung Heo, Gabseok Seo, Kyung Taek Cho, Yonghui Lee, Sanghyun Paek, Sung Kim, Minsu Seol, Seong Heon Kim, Dong-Jin Yun, Kihong Kim, Jucheol Park, Jaehan Lee, Lorenz Lechner, Thomas Rodgers, Jong Won Chung, Ju-Sik Kim, Dongwook Lee, Suk-Ho Choi, Mohammad Khaja Nazeeruddin published in Advanced Energy Materials, 2019.
• Controlling competing photochemical reactions stabilizes perovskite solar cells by Silvia G. Motti, Daniele Meggiolaro, Alex J. Barker, Edoardo Mosconi, Carlo Andrea Riccardo Perini, James M. Ball, Marina Gandini, Min Kim, Filippo De Angelis, Annamaria Petrozza published in Nature Photonics, 2019.
• Efficient perovskite solar cells by hybrid perovskites incorporated with heterovalent neodymium cations by Kai Wang, Luyao Zheng, Tao Zhu, Xiang Yao, Chao Yi, Xiaotao Zhang, Yu Cao, Lei Liu, Wenping Hu, Xiong Gong published in Nano Energy, 2019.
• Sensitization of silicon by singlet exciton fission in tetracene by Markus Einzinger, Tony Wu, Julia F. Kompalla, Hannah L. Smith, Collin F. Perkinson, Lea Nienhaus, Sarah Wieghold, Daniel N. Congreve, Antoine Kahn, Moungi G. Bawendi, Marc A. Baldo published in Nature, 2019.
• Development in utilizing singlet fission and triplet-triplet annihilation to improve solar cell efficiency thesis by Tony Chang-Chi Wu, Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
• Spontaneous Fluctuations of Transition Dipole Moment Orientation in OLED Triplet Emitters by Florian Steiner, Sebastian Bange, Jan Vogelsang, and John M. Lupton published in Journal of Physical Chemistry Letters, 2015.

ARTICLES AND BACKGROUND INFO

• Article by Tasshi Dennis, published in the IEEE Journal of Photovoltaics: A Novel Solar Simulator Based on a Supercontinuum Laser for Solar Cell Device and Materials Characterization
• Article by Mark. L. Brongersma, published in the NanoLetters: Light Trapping for Solar Fuel Generation with Mie Resonances
• Article by F. Wang, N. A. Melosh, published in the Nature Communication: Power-independent wavelength determination by hot carrier collection in metal-insulator-metal devices
• Article by Mark L. Brongersma published in the NanoLetters: Redesigning Photodetector Electrodes as an Optical Antenna

Measurement of the absorption/transmission properties of an optical fiber or a connector, or the dispersion of an optical fiber.

The most prevailing techniques used for fiber characterization using supercontinuum sources are absorption spectroscopy, SNOM/NSOM, and white light interferometry.

Publications

• T. Wieduwilt, J. Dellith, F. Talkenberg, H. Bartelt, and M. A. Schmidt, “Reflectivity enhanced refractive index sensor based on a fiber-integrated Fabry-Perot microresonator,” Opt. Express22, 25333-25346 (2014)
• Uebel, P. and Bauerschmidt, S. T. and Schmidt, M. A. and St.J. Russell, P.,”A gold-nanotip optical fiber for plasmon-enhanced near-field detection” Applied Physics Letters, 103, 021101 (2013), DOI:http://dx.doi.org/10.1063/1.4813115
• Lee, H. W. and Schmidt, M. A. and Tyagi, H. K. and Sempere, L. Prill and Russell, P. St. J. “Polarization-dependent coupling to plasmon modes on submicron gold wire in photonic crystal fiber“, Applied Physics Letters, 93, 111102 (2008), DOI:http://dx.doi.org/10.1063/1.2982083
• H. W. Lee, M. A. Schmidt, and P. St. J. Russell, “Excitation of a nanowire “molecule” in gold-filled photonic crystal fiber,” Opt. Lett. 37, 2946-2948 (2012)
• Patrick Uebel, Markus A. Schmidt, Howard W. Lee, and Philip St.J. Russell, “Polarisation-resolved near-field mapping of a coupled gold nanowire array,” Opt. Express 20, 28409-28417 (2012)