How can an inexpensive NeutronOptics Camera compete, and what more do you need ?
A large variety of CCD and CMOS detectors can be used, depending on application.
All cameras are supplied with software & high efficiency x-ray or neutron scintillators.
Try our ImageJ Barrel Distortion Correction macro & example image stack.
Notes on the kind of computer you can use including a Raspberry-Pi (Jesus Mendoza).
Fast CMOS X-ray or Neutron Cameras
Up to 120 frames/sec can be obtained with this new IMX432 CMOS camera using >10m USB3.2 cables. This is interesting for high intensity sources, usually x-rays, where short exposures (~10ms) can be sufficient. You don't need cooling for short exposures, and this simplifies camera operation, since only USB power is used, with a single cable. The camera can also be supplied with the 20 fps square IMX533 detector for the same price, when higher resolution and dynamic range are required with a lower frame-rate. With x3 SharpCap hardware binning of the IMX533 detector, up to 100 frames/sec can be achieved for 1000x1000 14-bit pixels.
This fast detector can also be used for smaller Fields-of-View with the mini-iCam or macro cameras
Large Cooled CMOS X-ray or Neutron Cameras
This 400x300mm camera, constructed for a large US neutron laboratory, uses a 36x24mm IMX455 CMOS detector coupled with a bright Nikon 50mm f/1.2 lens. It has high efficiency and low noise, allowing exposures of up to 10 minutes. By removing the horizontal extension, the FOV can be reduced to ~300x200mm, increasing both intensity and optical resolution. We recommend smaller FOVs of up to 250x200mm for lower flux sources.See the user manual for further details.
Small High Resolution Cooled X-ray/Neutron Cameras
This custom camera is based on our 1-CCD Laue camera, but uses a cooled CMOS detector for much faster read-out and higher resolution, while maintaining low noise for up to 10 minute exposures. The Field-Of-View (FOV) of up to 125x100mm depends on the choice of detector and lens. Otherwise, smaller camera boxes can be used with smaller lenses.An optional B4C/Pb neutron detector shield can be provided.
Compact CMOS x-ray or neutron cameras
USB powered CMOS detectors can be used instead of our "slim" CCD for both iCam and larger cameras. The CMOS iCam (right) like the compact iCam has ~25µM resolution over a 40mm FOV.
We can use the same compact CMOS detector in place of our usual "slim" CCD in any of our small x-ray or neutron detectors, such as the 100x100mm x-ray camera (left), increasing the resolution to 1920x1200 pixels, or ~85µM. (Real resolution depends on the scintillator).
High Resolution Tandem 1:1 and 3:1 Macro cameras
As an improvement to our 1:1 macro camera, we can propose a Tandem Macro option, using a 35mm f/1.2 imaging lens in front of the 100mm lens with a tiny IMX249 CMOS detector (5.86µ pixels). Both lenses are focussed to infinity to give a 3:1 macro image of our 50µ wire grid with <2µ pixels
x2 brighter than with our normal 1:1 macro camera.
We can use other tandem macro imaging lenses of different focal lengths depending on the required magnification and intensity. For example, this pair of Nikon Nikkor 50mm f/1.2 tandem lenses is x8 brighter than our normal macro camera, with the same 1:1 resolution. Maximising intensity is important when thin scintillators are used for the highest resolution. (Williams et al. and our Rodenstock camera).
Tandem macro lenses are claimed by PCO to be competitive in efficiency to fibre-optic bundles bonded directly to the chip, combining high efficiency with high resolution, but the FOV is small (~8mm diameter for our 1:1 Tandem Macro camera) .
The image on the right was obtained on the ILL NeXT D50 beamline from our Twin Nikkor 50mm 1:1 camera using a 10µ thick Gd2O2S:Tb/6LiF PSI/RC-TriTec scintillator with 6% of the light output of their 200µ scintillator. The inner circle shows that at least 25µ resolution was obtained for an exposure of only 3s with a neutron flux estimated to be ~5x10**7 n/cm2/s.
Gd2O2S is also a good x-ray scintillator. (Credits: Alessandro Tengattini & Lukas Helfen, ILL)
Controlling CCD imaging cameras via Ethernet & WiFi
Our small cameras can be supplied with slim GigE Power-Over-Ethernet CMOS detectors. Otherwise
we supply 10m amplified USB cables with all USB cameras, and they can be chained up to 30m. For our larger imaging cameras, we also offer a Raspberry Pi nano-computer as an interface with Atik Air software to allow remote control over Ethernet or WiFi.
It uses a 1.2 GHz 64-bit CPU with 1 GB RAM and is designed as an inexpensive (<€100) general purpose computer with Ethernet, WiFi, HDMI video and external USB storage, but we use it only as an interface.
Using our Scintillator Frames with Photographic Film
Our camera's scintillator frames can also be used for contact exposures with photographic film. The film is placed on the scintillator in a dark room and covered by our optional camera-frame back. The same scintillator can be used with either a CCD camera or film.
The bottom image shows the frame with a graph paper focussing scale covering the scintillator. Note the 5mm black B4C rubber seal around the inside of the frame, which normally presses against the camera flange to exclude light. The top image shows the optional film back, which is another 5mm B4C rubber seal on an aluminium plate. This smaller second seal fits inside the seal in the frame to exclude light. This second seal is filled with expanded polystyrene which presses the film gently against the scintillator.
The foam can be covered by a thin B4C layer to prevent thermal neutron backscatter.
(click images to enlarge them)
2D Honeycomb Collimators for Hydrogenous Materials
Thermal neutrons are strongly scattered by hydrogenous materials, and indeed such organic element contrast is the main advantage of neutron radiography over x-rays. But the scattered neutrons end up in the background, reducing contrast in the detector. Attempts have been made to use 2D honeycomb collimators to reduce such background. Although they are not sufficiently absorbing for fast neutrons, a 50mm long, 5mm wide cell collimator should work for thermal neutrons.
Fast lenses for Low-Light Imaging
At an Experts Meeting on Fast Neutron Radiography at FRM2 Munich in 2019 I mentioned the interest of using very fast lenses in my paper An Efficient Camera for Fast Neutrons. In the early days of x-ray scintillography for real-time medical screening, high aperture lenses were developed to minimise patient exposure to x-rays.Here we compare the 50mm f/0.75 de Oude Delft Rayxar (right) and Rodenstock TV-Heligon (centre) with a modern 50mm f/1.2 Nikon Nikkor (left). The Nikkor lens is used on our largest full-frame cameras, and bright f/1.4 Fujinon lenses on our most sensitive cameras. An f/0.7 lens should be x4 as bright as f/1.4. However, these old lenses have disadvantages.
There is no focus (or aperture) control, and the focal plane is only ~2mm behind the lens ! So even with a short 10mm back-focus, these lenses will not focus further than 500mm. And although the aperture may be f/0.75 with 2mm backfocus, increasing back-focus to 10mm reduces the effective aperture significantly. The micro-lenses on modern pixel-array cameras may also limit the solid angle seen by the pixels. These old lenses may be best used as objectives in a tandem lens macro camera, especially the lenses that incorporate a 90o mirror such as the Rodenstock "Heliflex", to take the detector out of the direct beam.
Large aperture C-mount lenses, such as the Fujinon 50mm f/0.7 and 25 mm f/0.85 were also once made for low-light video film cameras. These lenses are limited to image chips of up to 1" with very short back focus, and at full aperture are not very sharp, but may have some interest for low resolution imaging with very low light.
Modern compact lens mounts also use short back-focus distances, resulting in inexpensive large aperture f/0.95 lenses. For example, micro 4/3 lenses such as the Voigtlander 25mm f/0.95 have a back-focus of only 19.25mm, which makes it difficult to adapt such lenses to the M42-M54 threads on astronomy cameras with typically 12-18mm back-focus. However, a simple 4.5mm thick
micro-4/3 to M42 screw adapter can be made by bolting a bayonnet ring to a 1mm M42 ring. Less expensive alternatives, such as the SLR Magic 25mm T0.95 are made to imitate the soft video of cine-film, and together with others made by 7artisans and Mitakon Zhongyi, are of less interest for high resolution still imaging.
Test of a miniature x-ray imaging system
X-ray tomographic imaging with a miniature fine focus x-ray generator was recently tested at an international agency in Vienna. Our 125x100mm camera was used with a benchtop MOXTEK fine focus x-ray source and an inexpensive CAWO OG2 fine plastic x-ray scintillator. The palm-sized x-ray source was enclosed in the small shielded grey box (below). Operating at 30KV with a few micro-amps provided sufficient intensity for radiography with background radiation of <2mR/hr (similar to radiation levels in an aircraft cabin). Ease of use and low radiation levels are important for the intended use in training students.
With the higher power available from these miniature sources, with still minimal x-ray shielding, it would be possible to obtain geometrically magnified images of up to x10 by moving the object further from the scintillator screen. This requires a divergent beam and fine focus source to avoid image blurring. (AMETEK also make miniature x-ray sources, but with larger spot size). Other larger fine-focus generators such as the Oxford Instruments Ultrabright are also suitable. With high resolution scintillators in our macro camera, it would be possible to obtain micron-level resolution with high magnification from a divergent micro-focus source.
Fast Neutron Radiography with our Cameras
Fast neutrons (2.45MeV or 14MeV) are very much harder to detect than thermal neutrons because they are not captured by nuclei to provide ionising fission fragments. Scintillation in ZnS can however be achieved with knock-on protons rather than 6Li fission, though long exposures are needed. Fast neutron scintillators use high density polypropylene PP as a source of knock-on protons, and NeutronOptics now offer RC-TriTec PP-ZnS scintillators. Standard sizes are 75x50mm, 125x100mm and 250x200mm (smaller is more efficient).
Small D-D and D-T neutron generators are a promising development for low-cost neutron radiography, though the fast neutron flux is low. Even so, one of our 250x200mm cameras has already been used with an AdelphiTech 2.45 MeV D-D neutron generator to obtain radiographs with long exposures (~10 min).
The efficiency of the camera can be increased by a factor of x4 by reducing the FOV to 125x100mm, and can be further increased by a factor of x64 by binning pixels 8x8. Since the resolution after binning the smaller FOV will still be 360µm, this is still sufficient with the 2.5mm PP scintillators used for fast neutrons. The smaller camera is shown above. A cheaper compact version is also available.
Other clients from ETH-Zurich, PSI Switzerland and the Hungarian Academy of Science have recently used our smaller TS14 camera for fast neutron radiography and tomography at the 10 MW Hungarian reactor, using an 8 mm thick BC400 transparent plastic scintillator with spatial resolution of around 1.3 mm. It is remarkable that images were obtained through massive 30 cm thick lead shielding and filtering to attenuate gamma background.
An Experts Meeting on Fast Neutron Radiography at FRM2 Munich in October 2019 summarises progress, and includes our paper on An Efficient Camera for Fast Neutrons.
1-CCD Laue backscattering crystal alignment camera
We have developed various Laue crystal alignment cameras for x-rays, and similar cameras can be used with a neutron beam. They allow rapid crystal alignment, and can also be used for hands-on teaching of crystallography. A finely collimated white beam produces a number of "Bragg spots" from a single crystal, and by measuring the positions of these spots the crystal orientation can be determined. Greater precision is obtained with backscattering, but the intensities are weaker, especially for x-rays because of the scattering "form-factor". A classic bench-top x-ray generator with a spot size of ~1mm and power of 30-50 kV and 30-50 mA is required. The photo shows the 120x100mm camera, but a compact 100x80mm camera in a 200x120x67.5mm thick box is also available at the same price.
This inexpensive Sony 1" CCD backscattering camera is designed to replace the old Polaroid Laue camera, and has similar performance. A 1mm collimator traversing the camera directs the beam through a small hole in a mirror and out through the front carbon fibre window. The backscattered diffraction pattern from a single crystal 30 mm in front of the window is captured on a scintillator behind the window, and this pattern is reflected by the mirror to the lens-coupled CCD on top. The 1mm inner collimator can be simply pulled out to obtain courser 2mm collimation. A Si backscattered Laue pattern was obtained by Dr Dean Hudek at Brown University, and a
Sm2Fe17 pattern was obtained by Dr Léopold Diop and Prof W. Donner at the Technische Universität Darmstadt in only 2 minutes on a 1960's Philips generator (click to enlarge). For details, see the 1-CCD Laue camera manual
Tomography with NeutronOptics Cameras
Tomography requires the collection of radiographs with the sample rotated in the beam; specialised software is then used to reconstruct 3D images (13 MB) of the object and its interior. Both our standard high resolution imaging software, and our latest ImageJ-for-ASCOM software can collect hundreds of images, automatically, calling other Windows routines after each image to reset the sample position using eg LabView.For tomography, a precision sample turntable is needed to rotate the sample in increments of eg 0.5 degree between images. For samples of up to 30 Kg, we recommend the Newport Micro-Controle URS turntables which start at ~€2500, together with the SMC100PP motor controller (~€650) and SMC-PS80 power supply (~€93) and SMC-USB USB interface(~€63).
Anders Kaestner at PSI has developed free tomography reconstruction software tools.
The partial 3D reconstruction of a clock shown opposite was obtained from FRM-2 ANTARES data provided by Burkhard Schillinger. ImageJ was used to reslice the full reconstructed XY stack to XZ slices which were then displayed by imageJ's 3D_Viewer (low resolution GIF sample).
To learn about tomography, follow this MuhRec example, and read one of the free on-line books:
Principles of Computerized Tomographic Imaging
The Scientist Digital Signal Processing.
Big 500x400mm X-ray or Neutron Imaging Camera
We have made 400x300mm and even 500x400mm imaging cameras with a full-frame 36x24mm detector, such as the new Sony full-frame IMX455 CMOS chip, which with 9576x6388 pixels is capable of an optical resolution of better than 100 µm. The 500x400mm camera is a 2x2 scaled up version of our standard 250x200mm imaging camera, which itself is 2x2 times bigger than our compact 125x100mm camera (photos below). Remember that the efficiency of the camerta is proportional to the ratio of the sensor size to the FOV, so bigger cameras are less sensitive for the same sensor (and the scintillator costs much more).
Extended Camera for Radioactive Samples
Radioactive samples require special precautions to avoid damage to the CCD. Our solution is to use a telephoto lens to increase the optical path, so that the CCD section can be housed in a blockhouse several meters from the active sample, which can then be close to the scintillator to obtain the best resolution. This extended L-shaped camera is a stretched version of our 250x200mm "fast" camera. Relatively inexpensive 200mm or 100mm Canon or Nikon lenses are used, though these lenses with f/2.0 or f/2.8 are not as bright as our usual f/1.2 or f/1.4 lenses; an f/1.4 lens is x4 as efficient as an f/2.8 lens, but this camera is still fast enough for tomography on a low flux Triga reactor.Our "extended" camera has up to three 1000mm long front segments with an 800mm high vertical section holding the CCD, lens and mirror to give a maximum optical path of 3800mm, and a minimum of 800mm. Standard Canon or Nikon lens mounts are used, so it is easy to change the lens as well as the optical path.
(Click on the photos to enlarge).
All these cameras use a white neutron beam, and will work on either reactor or spallation neutron sources.
For further details of their application and availability, please contact
Alan.Hewat@NeutronOptics.com.