Building a Desktop Scanner part 2

drywall-screw-macro

I used an arduino mega, but any micro controller will do.  The mega has the advantage that it can take an inexpensive lcd display shield and still have lots of i/o pins easily accessible.  The arduino can’t safely drive a stepper motor directly so we connect it to a stepper motor driver.  I used an EasyDriver board which is inexpensive and lives up to its name.  The chip at the heart of the EasyDriver needs a heat sink to reach its maximum output, but in this application you probably don’t need one.  You won’t be running it very hard.  I run the arduino, the lcd and the EasyDriver all off a 9V battery.  This power supply somewhat limits the torque that the stepper will produce so if you are planning to turn a large turntable you might need a larger power supply and a heat sink on the driver.

The firmware is pretty simple.  One set of buttons allows you to select the number of exposures to make per revolution. One button starts and stops the scanner.  One button takes a single exposure and then rotates the stepper one increment.  This manual mode is handy with subjects which require each shot to be manually focused.

When I use the scanner I place it on a work table in my shop and mount the camera on a tripod next to it on the floor.  I use a cheap macro rail ($25 on amazon) to help position the camera.  The rail has more flex than is desirable, but it works okay since you aren’t actually touching the camera to trigger the exposure.  I use https://www.thingiverse.com/thing:548006 to hold a sheet of paper as a seamless background.  I also sometimes punch a hole in a sheet of paper and thread it on the stepper shaft to mask out the motor.  This approach might work well for you guys because you can cheaply replace the background if anything drips on it.

As you know lighting is critical for photogrammetry.  I use 3-4 JANSJÖ led desk lamps from Ikea to light the subject.  These lamps are very easy to position, and put out a lot of light.  They have small heads which makes it easy to light small subjects.  They are LEDs so they put out very little heat.  You can improvise diffusers with regular paper and tape.  Plus they are $10 each!  I also sometimes use a cheap LED ring light on the camera lens which provides nice diffuse light, but since it is attached to the filter ring of the lens it tends to get in the way with macro shots where the subject is almost touching the lens.

Another approach to lighting is to put the scanner inside a light tent.  This gives you a lot of diffuse even light and a clean background.  They sell small kits for photographing jewelry which are designed to minimize reflections and glare when shooting shiny things, so they might help with your stuff.  Also a circular polarizer filter would be a good thing to have on hand.  It can be helpful reducing glare.

 

2 thoughts on “Building a Desktop Scanner part 2”

  1. Hey guys! Thought I let you know I will be mentioning your cool little $50 3D scanner on ‘3D in Review’ this morning. $50 seems to be the sweet spot for DYI Photogrammetry eh? A nice complement to my cheap “Lazy Susan with a hole cut out or the middle” version. I think I might widen the hole now and add the stepper motor to it, for the best of both worlds. But I guess it becomes the $99 Photogrammetry table? I will bring it back on and talk about the mod after showing off your cool project. Now you have me thinking of adding a locking mechanism that either rotate at its center or locks the table and rotates the camera.

    I love to see great nifty low cost projects and it looks like you guys are wealth of knowledge and experience. In fact you are welcome to come as our “Guest Crashers” anytime. I bet you have ton of 3D stories to share.

    Anyway, great job and I will make your site one of my go to locations in the future.

    Thanks

    Mike Balzer
    Producer
    All Things 3D

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