Automated DSLR polarimeter

thingiverse

3D-printable automated polarimeter for DSLR cameras. <b>======== Background ========</b> A polariser filter is mounted in front of the lens, and photographs are taken at polarisation angles of 0,45,90,135 degrees. Stokes parameters S0-S2 can be calculated from these images, and used to calculate the angle of polarisation (AoP) and degree of linear polarisation (DoLP) for each pixel. <b>======== Design ========</b> The parts are designed for the Canon EF 50mm 1:1.8 STM lens. The openSCAD files can be modified for other lenses. I use a Canon EOS 7D (mark 1). I included holes for grub screws on the gear, but in the end the 3D printed part ft tight enough on the polariser to not need additional support. Z button rotates the polariser manually for zeroing. T button triggers the automated sequence of photographs at 0,45,90,135 degrees, followed by returning the polariser to the zero position. To zero the polariser, you can use the Brewster effect, i.e. light reflected from a non-metallic surface is horizontally polarised. http://cee.uma.pt/people/faculty/luis.gomes/laboptica/S13%20Anexo%20A%20Faq%20on%20polariztion%20componentes.pdf <b>======== Electronics ========</b> <center><i><b>*Before plugging the trigger into your camera, verify you have the correct voltages with a multimeter*</b></i></center> DSLR trigger is designed for canon cameras. The process is well explained by vec videos here: https://www.youtube.com/watch?v=Lq2goa40-mY Canon DSLR trigger is held at 3.3V, when pulled down the shutter is triggered. The circuit uses a voltage divider to achieve 3.3V. I used the A4988 stepper driver shield module in the final wiring for the control box. This was not included in the electronic schematics, but the wiring is the same. The schematic without the breadboard is the version that made it into the control box. <b>======== Parts ========</b> - Hoya 49 mm Pro1 Digital Polarised Circular Filter Amazon: https://www.amazon.co.uk/Hoya-Digital-Polarised-Circular-Filter/dp/B00P60ISNK ebay: https://www.ebay.co.uk/itm/184631987229?hash=item2afcec8c1d:g:qqwAAOSw49BemVkL&var=692353625746 - Mini Nema 11 Stepper Motor 28mm Body 1.8 Stepper Angle 0.8A 2 Phase 4-Lead. (Aka 28hd1411-02) https://www.amazon.co.uk/gp/product/B07PNV7RBW - Canon shutter https://www.amazon.co.uk/gp/product/B08B1KQMKJ - M2.5 bolts for stepper motor - M3 bolts - Arduino nano - Arduino nano terminal board. https://www.amazon.co.uk/gp/product/B093GQCWPG - 1kOhm and 2kOhm resistors - 100uF electrolytic capacitor - 2.1mm x 5.5mm Round Panel Mount Female Socket DC Connector. https://www.ebay.co.uk/itm/252080051894 - 2.5mm Mini Stereo Jack Chassis 3 POLE Panel Mount . https://www.ebay.co.uk/itm/352226275144 - A4988 stepper driver with shield https://www.amazon.co.uk/Youmile-Expansion-Stepper-DRV8825-Ramps1-4/dp/B07ZCQSQPQ - Momentary Mini Push Button https://www.amazon.co.uk/gp/product/B081TZFZVS - 12V power supply e.g. https://www.amazon.co.uk/TMEZON-100-240V-Converter-Security-Accessory/dp/B01FYPR5PS <b>======== Code ========</b> Arduino code, and polarimetic image analysis code available at: https://github.com/jacksupple/DSLR-polarimeter