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
David Prutchi won Design News’ prestigious “Gadget Freak of the Year” award for his development of the DOLPi diy Polarimetric Cameras.
David will present the DOLPi project at MD&M West in February 2017. The award will be presented at the Golden Mousetrap Awards Ceremony during the show.
Design News’ Golden Mousetrap Awards are part of UBM’s broader Anaheim event, North America’s most comprehensive design and manufacturing tradeshow and conference. Comprised of six shows and interrelated conferences from the company’s portfolio, the event includes Automation Technology Expo (ATX) West, Electronics West, Medical Design & Manufacturing (MD&M) West, Pacific Design & Manufacturing, PLASTEC West, and WestPack, and attracts more than 20,000 attendees.
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:
I was recently in Novosibirsk (Siberia, Russia) to run some clinical trials at the Meshalkin Novosibirsk Institute of Blood Circulation Pathology.
I took advantage of the opportunity, and made contact with fellow hardware hackers Eugene Mikhantiev (tall fellow with blue shirt in back) of the Akademgorodok NSU Hackspace, and Alexey Grischenko (brown shirt, sitting in front) of HackNsk. Eugene quickly organized a tour of the Incubator at Academpark, and a fun informal meetup with members of the hackspaces at the Technopark of the Novosibirsk Academgorodok.
I greatly enjoyed meeting you guys! Thank you Eugene for your kind and warm hospitality!
Click here for high-res picture.
I just posted a whitepaper containing complete construction details for two DIY imagers for the shortwave ultraviolet band. These UV converters can be used for RUVIS and Solar-Blind imaging applications.
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).
My new book “Exploring Ultraviolet Photography: Bee Vision, Forensic Imaging, and Other Near Ultraviolet Adventures with Your DSLR” is now available on Amazon for pre-order.
In this book, I will show you how to select equipment that allows you to capture otherworldly UV images. You’ll learn how to use filters that block visible light and prevent infrared light leaks and will discover how supplementing or overpowering sunlight with artificial UV light sources can help you create stronger images. You’ll also learn postprocessing techniques designed to enhance your UV photographs.
There is much to discover about the world as seen by bees, birds, and butterflies (and other creatures). I will take you into the wild to capture UV images that show how flowers advertise their nectar with beautiful markings to attract pollinating insects and birds. You’ll also discover how butterflies that look dull in visible light burst with intricate, iridescent patterns in UV.
Finally, you’ll learn about the scientific, medical, and forensic uses of ultraviolet photography.
From start to finish, this book will educate, inspire photographic creativity, and foster a better understanding of the UV world.
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.
Hackaday published an excellent article by Al Williams titled “The Grid Dip Meter: Forgotten Instrument”. This reminded me of an interesting physics experiment that really helped me back in college to understand the mechanism behind nuclear resonance. The experiment was described as a note in the American Journal of Physics in 1963: R.J. Blume, Demonstration of Nuclear Magnetic Resonance in Cobalt with a “Grid Dip” Meter, Am. J. Phys. 31, 58 (1963). Here is the text of that note (no figures accompanied it):
Demonstration of Nuclear Magnetic Resonance in Cobalt with a “Grid Dip” Meter
IBM Watson Laboratory, Columbia University,
New York 27, New York
THE nuclear magnetic resonance (NMR) absorption in ferromagnetic materials is tremendously enhanced compared with that in all other substances. By far the most intense NMR absorption yet reported is that of the Co59 nucleus in bulk cobalt.1• 2 At room temperature, the internal magnetic field at the cobalt nucleus is about 210 kG. The nuclei precess in this field at 213.1 Mc, and will absorb energy at this frequency from an rf oscillator coupled to the cobalt sample. No external magnetic field need be applied to the cobalt; a strong external field will in fact destroy the resonance.
All that is required to observe the resonance is some powdered cobalt, and a low-powered rf oscillator equipped with a meter which indicates grid current, i.e. a “grid clip” meter.3 Ordinarily, the tuned LC circuit of the oscillator is unloaded, and the grid current is relatively high. When energy is absorbed from the tuned circuit of the oscillator by a nearby resonant circuit, the grid current shows a dip. With a model 59 Megacycle Meter,4 the curved end of the tuning hairpin need only be held flat against the bottom of the bottle of cobalt. As the oscillator is tuned carefully through 213.1 Mc, a small clip of grid current will be observed. The absorbing “resonant circuit” in this case is the system of Co59 nuclei.
The 213.1-Mc resonance arises from nuclei of atoms located in the abundant face-centered cubic crystal structure. Nuclei of atoms in the less abundant hexagonal closepacked structure see a slightly larger magnetic field, and therefore resonate at about 221 Mc. 5 If a little cobalt is placed just inside the curved end of the hairpin, the 213.1-Mc absorption dip will become stronger, and it should then be possible to discern the 221-Mc absorption as well. Some weaker resonances are also present, but additional equipment is usually needed to see them. The 213.1-Mc resonance can be seen with the Heathkit model GD-1B grid dip meter.
A grid dip meter is normally coupled weakly to the circuit under test, in order to avoid mutual detuning, and the frequency dial is calibrated accordingly. The proximity of the bulk cobalt to the hairpin has two gross effects on the grid dip meter, in addition to providing resonant absorption of nuclear origin. Firstly, the added stray capacitance reduces the oscillation frequency by roughly 5 to 10% below that indicated on the dial. Thus, to obtain oscillation at 213.1 Mc when the cobalt is in place, the dial has to be set at some higher reading. The actual frequency has to be measured by standard techniques. 6 Secondly, resistive loading of the oscillator reduces the amplitude of the rf oscillation, and may stop it entirely if too much cobalt is brought too close. The best NMR sensitivity is obtained when oscillation is barely sustained.
Only the cobalt resonance is detectable by the means described here. The sample used in the present work was 300 mesh, assay 98% minimum, Ni 0.6%, obtained from the Fisher Scientific Company (catalog number C363).
1 A. C. Gossard and A. M. Portis, Phys. Rev. Letters 3, 164 (1959).
2 A. M. Portis and A. C. Gossard, J. Appl. Phys. 31, ZOSS (1960).
3 See any recent edition of the annual Radio Amateur’s Handbook (American Radio Relay League, West Hartford, Connecticut).
4 A grid dip meter manufactured by the Measurements Corporation, Boonton. New Jersey.
5 R. Street, D.S. Rodbell, and W. L. Roth, Phys. Rev.121, 84 (1961).
‘F. E. Terman and J.M. Pettit, Electrnnic Measurements (McGrawHill Book Company, Inc., New York, 1952), Chap. S.
The DOLPi Raspberry Pi-based polarimetric cameras received 5th place in the 2015 Hackaday Prize. Winners for this year’s prizes were announced on stage at the Hackaday Superconference on November 14, 2015.
The DOLPi project involved the development and construction of two low-cost polarimetric camera types based on the Raspberry Pi 2. DOLPi-MECH (and its productized IR-VIS-UV version DOLPi-UI) is a filter-wheel-type camera capable of performing full Stokes analysis, while the electro-optic based DOLPi-EO camera performs full linear polarimetric analysis at higher frame rate. Complete Python code for polarimetric imaging is presented. Various applications for the cameras are described, especially their use for locating mines and unexploded ordinance in humanitarian demining operations.
CLICK HERE for a complete project description including detailed construction instructions and Python code in pdf format.
The final version of the DOLPi whitepaper is now available here: DOLPi_Polarimetric_Camera_D_Prutchi_2015_v5