Three years ago I developed the DOLPi polarimetric cameras based on the Raspberry Pi. One used an electro-optical polarization analyzer, while the other used discrete polarization filters mounted on a filter wheel. The only issue with their performance was lack of speed. I mentioned back then that high-speed polarization imagers have been built using multiple sensors, each with its dedicated, fixed-state polarization analyzer. I finally got around to converting a 1980s-era three-tube camera into a real-time polarimetric imager. The full whitepaper with detailed step-by-step instructions is available for download in pdf format at: Converting_the_JVC_KY-1900_into_a_Real-Time_Polarimetric_Imager_-_Prutchi_2018
After many years of use, the image intensifier tube (IIT) in the image intensifier system that I use for my experiments in quantum physics developed some nasty half-moon shadows in the periphery, so I decided to rebuild it with another MX-10160-type IIT. I documented the build in the following document: diy Image Intensifier System Prutchi
I recently purchased a Seek RevealPro Thermal Camera, which boasts a 320 x 240 thermal sensor with >15 Hz frame rate at an incredibly affordable price.
One of the only issues that I have with this camera is that it comes with a fixed 32° field-of-view lens. This is OK for general thermal inspection, but it’s a real disadvantage when trying to use the camera for close-up work to assess dissipation on printed circuit boards, or for identifying a faulty or undersized component. On the opposite side of the distance range, the 32° FOV lens makes it difficult to see and measure the temperature of objects at a distance, or of smaller objects at normal distances.
I thus decided to build magnifying (“macro”) and close-up (“telephoto”) converters for the RevealPro. I’m passing along information on my designs in hopes that others will find it useful. You can read the post at http://uvirimaging.com/2018/03/05/thermal-camera-diy-macro-and-telephoto-converters/ and get detailed instructions in the following whitepaper: Diy-Thermal-Camera-Telephoto-Converter
I just posted a new whitepaper with a short primer on UV Fluorescence Photography and a diy 18W, 3-wavelength, professional-grade lamp.
The figure above shows pictures of Hackmanite from Bancroft, Ontario, Canada taken using this diy lamp: a) White light photograph; b) reflected near-UV with Baader-U and long-wave illumination; c) fluorescence with wideband (LW, MW and SW) excitation; d) long-wave UV excitation; e) fluorescence with mid-wave UV excitation; f) fluorescence with short-wave UV excitation.
The whitepaper is available at: http://uvirimaging.c…ce-photography/
For more diy UV photography and imaging projects, check out my new book:
Reader Paul Wallace contacted me to tell me about the DOLPi electro-optic polarization camera that he built for his iPhone. His ingenious solution makes use of the iPhone’s flashlight to calibrate and synchronize the control of the polarization analyzer (hacked from a welder’s mask as described in the DOLPi whitepaper).
Andrew Gliesman sent me these pictures of his DOLPi Visor replication along with a very kind note.
…I wanted to thank you for your excellent paper on the DOLPi Polarimetric Camera. The amount of technical detail combined with providing a solution of a real world humanitarian problem made it special to me.
I recently built a DOLPi Visor and wanted to share my alternative form-factor with you (see photos.) With respect to the build notes, everything was spot on – I just found that I needed to clean the adhesive residue after removing a polarizer film on the LCP (perhaps this had to do with the brand – I couldn’t find the MASK brand on Amazon.)…
The point about the adhesive is interesting. Indeed, the adhesive remains transparent after removing the polarizer film, but becomes cloudy if scratched. I found that the best way to remove it is to loosen it with a drop of “Goof-Off” and then scraping it with a sharp razor blade.
DOLPi – A Low-Cost RasPi-based Polarization Camera
A polarimetric imager to detect invisible pollutants, locate landmines, identify cancerous tissues, and maybe even observe cloaked UFOs!
The polarization of light carries interesting information about our visual environment of which we are usually unaware. Some animals have evolved the capability to see polarization as a distinct characteristic of light, and rely critically on this sense for navigation and survival. For example, many fish, amphibians, arthropods, and octopuses use polarization vision as a compass for navigation, to detect water surfaces, to enhance the detection of prey and predators, and probably also as a private means to communicate among each other.
While we have used technology to expand our vision beyond the limits of our ordinary wavelength and intensity sensitivities, the unintuitive nature of polarization has slowed down the development of practical applications for polarization imaging. Polarization cameras do exist, but at over $50,000, they are mostly research curiosities that have found very few practical uses outside the lab.
The DOLPi project aims to widely open the field of polarization imaging by constructing a very low cost polarization camera that can be used to research and develop game-changing applications across a wide range of fields – spanning all the way from environmental monitoring and medical diagnostics, to security and antiterrorism applications.
The DOLPi polarization camera is based on a standard Raspberry Pi 2 single-board computer and its dedicated 5MP camera. What makes the DOLPi unique is that the camera sits behind a software-controlled electro-optic polarization modulator, allowing the capture of images through an electronic polarization analyzer. The modulator itself is hacked from two low-cost auto-darkening welding mask filters ($9 each). In spite of its simplicity, DOLPi produces very high quality polarization images.
This is a first-of-its-kind project! I am not aware of any polarization imager ever presented as an enthusiast-level DIY project, yet it holds truly awesome disruptive power for the development of brand new scientific and commercial applications!
A complete description of this project in pdf format is available at: DOLPi_Polarimetric_Camera_D_Prutchi_2015_v2
Sphere Research is clearing out all the Philips PMT assemblies they have in stock to empty their expensive off-site rental storage space. While stock is available, you can order any PMT shown as a Philips Medical Systems assembly at the beginning of this page for only $25 +shipping:
Simply identify the deal as coming from DIY Physics when ordering (Note from diyPhysics.com: nothing in it for us except passing along some great info…).
All these tubes will be cleared out shortly so they can close down their over-priced off-site rental storage space. The offer is limited to stock on hand at the time of order. Sphere Research is happy to consolidate orders and help you minimize shipping costs wherever possible. They can take Visa, MasterCard and PayPal for orders. These are very high performance tubes and hard to find, but they are very awkward for them to store in the big factory boxes, so they have to go.
Javier De Elias Cantalapiedra from Madrid, Spain posted the YouTube video above to show the e/m measurement system that he put together based on the description in our book. His measurement system is based on Hoag’s method, and his nicely laid-out setup allowed him to obtain very nice results (4 to 6% error compared to the theoretical e/m).
Javier is an industrial engineer who works in the telecommunications industry. However, his passion is physics, which he pursues at a (very high) amateur level.
Thank you Javier for sharing!
I HAVE NO RELATION TO SELLER – Just passing along in case someone is interested.
eBay item number 271206242864:
“The EG&G (or Perkin Elmer) SPCM-AQR is a self-contained module which detects single photons of light over the wavelength range from 400 nm to 1060 nm and sensitivity which often outperforms PMTs. The option 13-FC indicates 180 micron diameter Si APD, Dark Count < 250cps and FC connector attached.
I obtained this detector in working order five years ago and have not used it since then. The detector comes with two unknown optical fiber cables (one end: FC, the other end: bare fiber) and a supply cable to which you need to give 5V. No manual included. The US sale only.”
One of my all-time favorite circuits is the the following DC-to-AC inverter (click diagram to enlarge) based on an old color TV flyback:
A very interesting article by Bernhard Wittmann, Sven Ramelow, Fabian Steinlechner, Nathan K Langford, Nicolas Brunner, Howard M Wiseman, Rupert Ursin,and Anton Zeilinger, entitled “Loophole-free Einstein–Podolsky–Rosen experiment via quantum steering” appeared in the Nature’s New Journal of Physics, Volume 14, May 2012.
This paper describes a Bell’s Inequality Violation experiment in which the “fair sampling” loophole has been closed. This loophole posits the possibility that classical – rather than quantum – effects could be responsible for measured correlations between entangled pairs of photons in a Bell’s Inequality Violation experiment. The paper’s abstract reads:
“Tests of the predictions of quantum mechanics for entangled systems have provided increasing evidence against local realistic theories. However, there remains the crucial challenge of simultaneously closing all major loopholes—the locality, freedom-of-choice and detection loopholes—in a single experiment. An important sub-class of local realistic theories can be tested with the concept of ‘steering’. The term ‘steering’ was introduced by Schrödinger in 1935 for the fact that entanglement would seem to allow an experimenter to remotely steer the state of a distant system as in the Einstein–Podolsky–Rosen (EPR) argument. Einstein called this ‘spooky action at a distance’. EPR-steering has recently been rigorously formulated as a quantum information task opening it up to new experimental tests. Here, we present the first loophole-free demonstration of EPR-steering by violating three-setting quadratic steering inequality, tested with polarization-entangled photons shared between two distant laboratories. Our experiment demonstrates this effect while simultaneously closing all loopholes: both the locality loophole and a specific form of the freedom-of-choice loophole are closed by having a large separation of the parties and using fast quantum random number generators, and the fair-sampling loophole is closed by having high overall detection efficiency. Thereby, we exclude—for the first time loophole-free—an important class of local realistic theories considered by EPR. Besides its foundational importance, loophole-free steering also allows the distribution of quantum entanglement secure event in the presence of an untrusted party.”
We prepared a short note on how to build a dynode voltage divider network for inexpensive surplus XP2422/SN photomultiplier tubes. The XP2422/SN PMT is especially suited for gamma-ray spectral analysis when coupled to a NaI(Tl) scintillation crystal because of its high pulse-height resolution (PHR). The XP2422/SN is available from Sphere Research in Canada.