Invisible QR Code Navigation for Robots 2020

This is a invisible code fresh from the printer, in the picture the ink has not dried yet, so you can clearly see that some thing was printed there. 

Using a 405nm LED on this code we get a bright and easily readable code, also the same code can be printed in the same area and lit with 780 nm IR and wold show as grey through a camera without an IR filter.

Using a workforce Epson W3700 printer I used fake ink cartridges and chips that trick the printer into thinking that the cartridges are genuine epson and also that the inks inside the cartridges are the correct type. In addition the chips also also never report empty, instead each time they are removed and re added they show full. This is very useful because these cartridges have rubber plugs that can be opened and refilled with the desired invisible ink.

I conclude printing the code was a great success that did not offer any issues once the printer was setup with the custom cartridges. My next test will be printing these onto clear matt stickers for use on the floor as well as furniture and other objects to be discretely marked.

Here are two baggies of up-shift crystalline phosphors with a IR laser directly illuminating them, they are really bright ,but the IR laser is actually invisible to the human eye. It is important to note that you need to keep the power down on a IR laser well below 5 mw, preferably around 1 mw because your eyes will not blink in response to the bright laser emission. One way I intend on lowering the output is PWM, second is to put a star filter over the diode to disperse the laser light in a much wider area making it more useful to illuminate the QR codes.

https://en.wikipedia.org/wiki/Stokes_shift

"If the emitted photon has more energy, the energy difference is called an anti-Stokes shift;^[5] this extra energy comes from dissipation of thermal phonons in a crystal lattice, cooling the crystal in the process. Yttrium oxysulfide doped with gadolinium oxysulfide is a common industrial anti-Stokes pigment, absorbing in the near-infrared and emitting in the visible region of the spectrum. Photon upconversion is another anti-Stokes process. An example of this later process is demonstrated by upconverting nanoparticles."

crystalline latices powdered pigments can augment existing ink carriers so that invisible codes, glyph or even April codes can be excited by a laser indoors.

So in efforts to both save power and also get better range for the QR scanning, I planned to swap and test out lasers as a light source to excite the up conversion pigments in the invisible QR code instructions.  Both IR and UV are very faint in the visible eye , but when they hit a pigments that up shift they release electrons in the visible spectrum, pretty cool right??

A variety of florescent particulate can be combined with Up Conversion IR inks in order to take a otherwise invisible bar code or QR code into a visible glowing readable beacon of light for robotics navigation and programming. In my case my application is both unique and useful. I regularly search for similar information about invisible marking methods like those in anti counterfeit measures.

https://phys.org/news/2012-09-upconverting-nanoparticle-inks-invisible-qr.html

Here is the first time I have seen this used specifically in the way that I have, but the specifics are kept secret, the postal service sometimes has UV reactive codes come through that use information to track mail outside just the address info.

https://hackaday.io/project/160641-wearable-ir-led-modulated-human-pet-tracking

https://hackaday.io/project/160641-wearable-ir-led-modulated-human-pet-tracking

OK, so the first prototype started on a full side  Roomba with a bluetooth type controller with a 2.4ghz analog camera. I don't think this camera works anymore because the battery has lived it's life so I am moving to another setup for the second go around.

Three prototype Invisible QR code readers version 2

Ceiling View NAV Sensor

This is the original intent of the QR code navigation , but the utilization does not stop here. Also not everyone has a ceiling within height they have access to apply a QR code. In that case walls or floors even may be more useful. Even 12 foot ceilings can use the vertical QR NAV beacons.

Forward View NAV Sensor

These are the most straight forward navigation beacons. Everything from doors, doorway edges, or even charge docking. They could be placed on elevator doors and under the elevator call button for service robots.

Floor Facing Macro View NAV Sensor

Though this is the least obvious, businesses or homes with smooth floors like tile, wood or even concrete can use this method. It also would work on sidewalks, driveways and roads. This version of the sensor can clearly focus on codes .5 inches away and .25 inches in size. TINY RIGHT!?

So the robot arrived, if you don't mind having no instructions whatsoever and nothing lining up then this is the kit for you. It took a few tried before I found holes that would work for two layers but they are not symmetrical.  The package was for two turtle bots ,but the package was ripped open and much of the hardware missing. There is no labeling on these either.  I may rethink using this as a test platform and 3D print something to go on top of the rover 5 4x4 with encoders instead. We will see and I will update you.

The frame I ordered for testing purposes appeared to finally arrive. The package was damaged and likely some pieces are missing. I will start assembly so I will have a platform to start playing with.

Here I could have used a extra pair of hands , but it was just a quick test before bed after filling cartridges. I overplayed the IR ink onto the UV and the contrast really pops! Much better that IR on white paper by itself, when UV  light is off you can see the camera picks up the IR ink on white paper as dark gray. Remember the longer term is invisible tags which in most cases means clear or Matt clear adhesive labels on printable sheets.

The pictures loaded in weird places on my phone so I will fix that tommorow on a pc.

IR only with the IR camera-

I filled cartridges will all the inks I have. I am likely to use noodlers and the UV absorbing ink , but I will start testing different labels soon. I picked up a Epson Workforce printer that uses these cartridges for 89 dollars from Office Depot. I believe I will dedicate the printer to making these invisible tags as to not mix inks.

Noodlers White versus UV yellow, very close , but the yellow is 5 times the cost!