Frequently
Asked Questions
FAQs about our products and technology
Do you have any questions about our technology or products?
Please consult the frequently asked questions below.
Welcome to the FAQ section of NIREOS where you’ll find answers to common inquiries about our high-tech spectroscopy products, such as HERA hyperspectral cameras, GEMINI interferometers and SPIDER spectrometer, as well as general information about our business.
GENERAL
I’m interested in joining the NIREOS team, how can I apply?
Thank you for your interest in joining our team! Please visit our ‘Work With Us’ section for information on current job openings and how to apply.
I want to join your network of distributors, how can I do that?
Thank you for your interest in joining our network. If you would like to become our partner, please feel free to contact us at info@nireos.com. In your message, we encourage you to share information about your company, the territories you cover, and your current range of products. Additionally, any other relevant information you think would be helpful for us to know is welcome.
I’m not sure which product is the most suitable for my case, what can I do?
You can contact us by filling out our contact form, and we will be glad to discuss your application with you and suggest the best product for your needs.
How can I get in touch with a distributor?
NIREOS products are marketed and sold worldwide through our local offices and a global distribution network. By filling out our contact form, your request will be automatically forwarded to the distributor that matches your needs in terms of product and location.
Can I receive a demo unit?
Yes, NIREOS is keen to provide demo units to users that would like to test our products. Please contact us at info@nireos.com to schedule a technical call for discussing possible implementation of our devices in your setups and plan a demo at your facility.
GEMINI and GEMINI-2D Interferometers
Is GEMINI the same as a TWINS interferometer?
Yes, the GEMINI-2D is the commercial version of the advanced TWINS birefringent interferometer technology. The GEMINI interferometer, instead, is based on the simplified version of the TWINS.
What is the difference between TWINS and GEMINI?
TWINS (Translating-Wedge-based Identical pulses eNcoding System) is the patented optical technology developed at the Politecnico di Milano that underlies our GEMINI interferometers. While TWINS refers to the scientific name and its original development, GEMINI is the commercial name of our compact, robust and fast FT spectrometers that utilise this innovative technology.
What is the difference between GEMINI and GEMINI-2D?
GEMINI and the GEMINI-2D share the very same working principle – i.e., use wedged-shaped birefringent crystals to generate a variable and phase-locked delay between two orthogonally polarized light replicas. The difference between GEMINI and GEMINI-2D is the way they handle the incoming pulse.
The GEMINI creates two pulses with a relative variable delay, see animation below.
However, while changing the relative delay (i.e., while moving a birefringent wedge), the total thickness of material crossed by the light also changes. This has two main consequences:
- the absolute arrival time of the two pulses after the interferometer is not fixed. The relative delay between the replicas changes while scanning the moving wedge, but this also changes the absolute arrival time of the two pulses. Indeed, the pulses in the animation both move during the scan.
- in the case of ultrashort laser pulses, changing the thickness of the material leads to a change in the dispersion (and therefore, the duration) of the pulses after the interferometer. In other words, your pulses will change their duration during a scan.
These consequences do not have any impact in those experiments where the GEMINI is placed after the sample (i.e., after the light-matter interaction) or if you do not work with ultrashort laser pulses (such as in fluorescence, either steady state or time resolved). In these cases, the GEMINI is the best option.
The GEMINI 2D has two additional birefringent elements (see the animation below), to keep constant the thickness of material crossed by the light during the scan of the interferometer.
This enables one to keep fixed the absolute arrival time of one of the two replicas (with attosecond stability). Moreover, it keeps constant the dispersion introduced during the scan of the delay between the two replicas, so that the pulse duration is preserved during the scan. This enables one to insert the GEMINI 2D before the non-linear interaction at the sample. The typical experiment where you need these features is 2D spectroscopy (and that is why the name, GEMINI-2D!).
Can the GEMINI select a specific spectral band?
No, the GEMINI Interferometer does not act as a monochromator, so it is not possible to select a single wavelength at the output, given a broad spectrum in the input.
The GEMINI Interferometer always transmits the entire spectrum of the incoming light, introducing a spectral modulation with a period that depends on the delay of the interferometer.
For more information on the working principle of the device, please refer to the video below.
Is it possible to reduce the spectral bandwidth to decrease the measurement time?
No: due to the employed Fourier-transform approach, there is no trade-off between the working spectral range and the measurement time. However, if one is interested in measuring in a narrower spectral range, it is possible to reduce the measurement time by undersampling the interferogram. One should notice that this might introduce some aliasing effects if not handled properly. For more information on this topic, please contact us directly. Please note that the measurement time is also affected by the spectral resolution that you want to achieve, i.e., the better the spectral resolution, the longer the scan of the interferometer and thus the measurement time.
How can I choose the most suitable version of GEMINI for my application?
There are three categories of possible options:
– Spectral coverage
The standard model of GEMINI covers the range 400 nm – 2300 nm. There is the option of upgrading it to cover a much broader region (250 nm – 3500 nm). On request, GEMINI can be customized to cover the 500 nm – 4200 nm range.
Moreover, currently NIREOS is developing a special version of GEMINI, which can work up to 15 microns. Stay tuned for updates on this version!
– Speed
You can select one out of two versions of the driver that controls the relative delay between the two generated replicas of light (“standard” and “high performance – HP”). With respect to the standard controller, the HP version guarantees a higher speed of the scan (up to 5 time faster: it typically takes 15-20 millisecond per step in a step-scan mode) and a much higher accuracy and stability in the relative delay (on the order of 1 attosecond – that is more than 1000 times better than the optical cycle of visible light). This ultimately translates into a much better signal to noise ratio of the retrieved spectrum of your signal.
When GEMINI is coupled to SPAD, APD or PMT detectors and TCSPC systems to detect time-resolved and very weak signals, we always recommend to go for the HP version.
– Spectral resolution
You can select one out of two versions (S, L) with different spectral resolutions:
Please note that this is the minimum achievable spectral resolutions for each version; if sometimes you do not need such a good spectral resolution, you can perform shorter – and thus faster – scans (these parameters can be easily selected via software) and get a worse spectral resolution.
– Only for GEMINI-2D: symmetric or asymmetric version
The difference between the asymmetric and symmetric version is the way in which the moving replica is scanned in time around the TIME ZERO. In the symmetric version, the delay T1 can be varied from –T to T. In the asymmetric one the delay T1 can be varied from –δT to 2T (approximately). This means that you can achieve a higher spectral resolution (longer scan) with the asymmetric version. In general, the symmetric version is only used in niche applications, where it is used as a delay line. For all the other applications, we recommend the asymmetrical version.
Does the GEMINI work with coherent (i.e. lasers) or incoherent (i.e. lamps, fluorescent samples) light sources?
The GEMINI Interferometer can work in both cases.
Can I perform experiments with ultra-short laser pulses using the GEMINI?
If the GEMINI is placed “after the sample” (i.e. when the light has already interacted with the sample), then it is possible to use it with ultra-short laser pulses, as it does not affect the temporal resolution of your experiment. As an example, you can refer to this application in pump-probe spectroscopy. [F. Preda et al., “Broadband pump-probe spectroscopy at 20-MHz modulation frequency“, Opt. Express 41, 2970-2973 (2016)]. In this configuration, the use of the GEMINI is particularly advantageous when combined with high modulation frequencies.
Instead, if you need to use the interferometer before the sample, then the GEMINI-2D is the most suitable device. As an example, the GEMINI-2D is used in bidimensional electronic spectroscopy (2DES), in which it creates two replicas of ultra-short pump pulses with a precise control on the dispersion.
How to couple the GEMINI with time-correlated single-photon counting (TCSPC) modules?
If you are interested in measuring time- and frequency- resolved fluorescence (TRES), we can provide a plug&play software that directly enables the control of both the GEMINI and the TCSPC card, so that you can easily acquire a TRES map without any extra effort for integration. For more information, please check this application note.
The GEMINI is compatible with the following TCSPC cards:
Becker & Hickl GmbH:
• SPC-130-EMN (Tested).
• SPC-150 (Tested).
• All SPC family board (Compatible).
PicoQuant GmbH:
• PicoHarp300 (Tested).
• PicoHarp330 (Tested).
• TimeHarp260 (Tested).
• HydraHarp400 (Tested).
• MultiHarp150 (Tested).
Swabian Instruments GmbH:
• Time Tagger 20 (Tested).
• All Time Tagger boards (Compatible).
Tediel:
• Felix (Tested)
Universal Quantum Devices:
• Logic16 (Tested)
If you have a different TCSPC card, do not hesitate to contact us at info@nireos.com for more information.
Is there a dedicated Software? How does it work?
The GEMINI comes together with a plug&play software, which allows one to easily control the device, acquire the data of interest and retrieve the calibrated spectrum of the light.
The software is open access and described by a detailed manual, so that it can be freely modified by the user according to his needs. Moreover, NIREOS team is always available to help the user for customization, if needed.
How does the Optical Alignment work?
The GEMINI Interferometer has a 10 mm clear aperture, and the light inside the device propagates in free space. The most efficient way to use the GEMINI is to enter with collimated light. If one uses optical fibers, then it is possible to use fiber couplers before and/or after the GEMINI. The optical alignment of the GEMINI is straightforward, as you just need to insert it into the beam path in your setup.
Which is the provided Spectral Resolution?
The spectral resolution provided by the GEMINI Interferometer is not constant as a function of wavelengths, but it increases at longer wavelengths. This behaviour is due to both the Fourier Transformation approach and the birefringence, which depends on the wavelength. Please refer to the following graph:
The graph above shows the best spectral resolution achievable by the two standard versions of the GEMINI Interferometer (S and L versions). Please note that the GEMINI offers the ability for customers to adjust the spectral resolution simply via software: the user can even decide to perform faster measurement with lower spectral resolution. A change in the spectral resolution does not affect the optical throughput of the device.
HERA Hyperspectral Cameras
Is HERA a push-broom or a snapshot hyperspectral camera?
HERA is not a push-broom, nor a filter based or a snapshot hyperspectral camera. It works with a staring approach, based on Fourier Transform. HERA embeds an ultra-stable and compact interferometer in front of a bidimensional sensor. This approach guarantees very high light throughput and a variable spectral resolution (easily adjustable via software), without compromising the spatial resolution.
The HERA can be easily mounted on a tripod, without the need to move the sample or the camera to acquire the hyperspectral image. The acquisition time of an entire hyperspectral cube is approximatively 10-30 seconds, depending on the chosen spectral resolution and illumination intensity. During this time, the sample and the camera should remain static with respect to each other. You can check the HERA hyperspectral camera tutorial below.
How many Spectral Bands does it measure?
Unlike other hyperspectral cameras based on spectral filters or dispersive elements, with the Fourier Transform approach the number of bands does not depend on the hardware. In fact, as the spectrum at each pixel of the image is the Fourier Transformation of the interference signal, it is a continuous function (or curve). Of course, when plotting the data, one needs to sample the spectrum with a proper number of points. The number of points is chosen to match the actual spectral resolution of the measurement, which depends on the chosen Scan Mode.
What is the spectral resolution of the HERA?
There are three predefined interferometric scan modes (S, M, L) selectable via software. These determine the spectral resolution of the HERA. Please refer to the following graphs for the spectral resolution provided by the HERA depending on scan length:
The spectral resolution provided by the HERA is not constant as a function of wavelengths, but it increases at longer wavelengths. This behaviour is due to both the Fourier Transformation approach and the birefringence, which depends on the wavelength.
Which is the typical measurement time?
HERA requires a few tens of seconds to capture the image of the scene and provide the hyperspectral data-cube. The measurements time depends on the integration time, number of averages and the chosen resolution. Under low illumination conditions or by selecting a high spectral resolution, the acquisition time could be longer.
What is the HERA field of view (FOV) and how can I estimate the spatial resolution?
You can calculate the horizontal FOV as :
where d is the distance between the camera and the sample and α is the angular FOV. If you want to know the dimension of the vertical FOV, you just need to consider that the ratio H/V is 0.8. For example, with the HERA VNIR at the minimum working distance (d=100 cm), you have a FOV of 14×11 cm. With the HERA SWIR at the minimum working distance (d=150 cm), you have a FOV of 29×23 cm.
The spatial resolution can be estimated by dividing the FOV for the number of pixels of the camera: 1280×1024 for the HERA VNIR and 640×512 for the HERA SWIR. At the minimum working distance, the spatial resolution of the HERA VNIR is 110 µm, HERA SWIR 450 µm.
The FOV can be duplicated or reduced (MACRO imaging) using additional lenses supplied by NIREOS. With the lens to duplicate the FOV, the angular FOV is simply duplicated. With the MACRO lens, the working distance is reduced and fixed to ~20 cm and the FOV to ~ 3 × 2.5 cm (H × V).
What is the working distance of the HERA?
HERA VNIR has a minimum working distance of 1 m and can go to infinity. HERA SWIR has a minimum working distance of 1.5 m and can go to infinity.
Can the HERA be mounted on a microscope?
HERA can be attached to any microscope that have a C-mount port, by simply adding an optomechanical adapter designed by NIREOS. Please note that the optical performance of the camera depends also on the optics inside the microscope! Please contact us at info@nireos.com for more information.
Can other optics be mounted in front of the HERA?
HERA already embeds a lens (not interchangeable) and is equipped with a SM1 threaded input on which additional lenses supplied by NIREOS can be mounted. For example, lenses are available to duplicate the FOV or perform MACRO imaging. An additional accessory allows also to mount 1-inch filters in front of the camera.
What are the illumination requirements?
Due to its extremely high sensitivity, HERA can work under low-light illumination conditions. This advantage is a consequence of the Fourier transform approach, as the employed interferometer (and the absence of the entrance slit) guarantees a high throughput. The camera is therefore very well suited in those applications in which intense and powerful illumination sources are not allowed, as they would damage the sample, such as in biology or cultural heritage. For example, HERA hyperspectral camera is so sensitive that it can measure hyperspectral images of the fluorescence signal emitted by a sample.
It is strongly recommended to use a light source working with DC. If the light source does not work with DC (i.e., works with AC) it is suggested to set the integration time of the camera equal to the period of the AC illumination to avoid possible artifacts.
What would be the minimum specifications for a laptop/computer to handle HSI datasets? How does the software work? Which OS are supported?
The minimum specifications for a laptop/computer capable of handling HSI datasets are at least 32 GB RAM and a fast processor. An SSD drive is also suggested.
HERA comes with two software packages: one to acquire the hyperspectral images, see a preview of the measured data and save the measurement to your computer, and the other for a deeper data analysis.
The OS supported is Windows.
What data formats can be exported by the software?
The software can export data in ENVI (flat-binary raster file with an accompanying ASCII header file) or MATLAB format.
Is it possible to have sample dataset?
Yes, please contact us at info@nireos.com for more information and access information.