Readers' Challenge: QR Code 3mm Solution Needed

small_QR_CodeA subscriber to The Bar Code News has asked for help to find a solution for his business. We, in turn, are asking our readers – who, we contend, include the most adept and ingenious bar code professionals in the world – to apply their gray matter to this problem, and post an answer demonstrating their erudition in the comment section below. Respondents with answers are invited to shamelessly plug their company or service at the same time.

Up for a little challenge? Read on:

The subscriber’s company makes small metal parts and wants to have a 3mm by 3mm QR code laser etched on to the parts. The QR code will contain a 15 digit alphanumeric code for that part. (Each identical part will contain the same number. No serialization involved.) This is the first part of the problem. Can you recommend a vendor to do this marking?

The second part of the problem – the company wants their salespeople to be able to scan that 3mm x 3mm code with their smartphones, presumably for an inventory/ordering process. 3mm is 0.11811024 inches, according to my calculator.

Thus far, getting their smartphones to scan codes that small has been a problem for the company. I do not know which Smartphone app they are using. Nor do I know if the printer they are using to create and test those codes is up to the task.

Should their smart phones be able to read a 3mm QR code with 15 characters embedded in a code that size? If not, what model of imaging scanner would be good for use in the field?

Can you – the savvy reader – offer an approach, based on experience, to finesse this predicament? If so, the comment section (and acclaim and immortality) awaits below.


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Darryl Zurn
0 #9 Darryl Zurn 2011-12-16 15:38
NASA has had to do this for many years, and have an excellent reference covering all kinds of Direct Part Marking.

Search for NASA's free technical standard NASA-HDBK-6003C

Bret daCosta
0 #8 Bret daCosta 2011-12-15 07:46
Hello Steve O, I am not sure it will scan reliably after laser etching on small metal parts.I tested the scan directly off of my computer screen using a Samsung Galaxy equipped with the newest version of the Microsoft Tag Reader. It took a very steady hand but it did scan. It has been my observation that all smartphones are not equal in the ability to scan tiny codes.Question: Have you downloaded the latest version of Tag? It was released just 48 hours ago and also reads QR. Thank you for your comment. d
Steve O
0 #7 Steve O 2011-12-15 07:17
From what I have tested, no smart phone has the hardware to scan a 3mm 2D code right now. It might be worth trying a Macro Cell Lens Band from Photojojo (or similar) to see if that helps, but otherwise I think you would have to use industrial hand scannners.
Steve O
0 #6 Steve O 2011-12-15 06:39
Sorry to disappoint you 'Tag Master', but having tried a hi-res print of a 3mm MS Tag, along with QR Code and Datamatrix, it doesn't scan with a smart phone at all. Test it before you go in with the marketing spiel.
Craig Aberle
0 #5 Craig Aberle 2011-12-14 13:01
This comment was posted by John O'Brien on another page and is re-posted with his permission:

First step, unless the product is for use in Japan exclusively, I would switch to Data Matrix. Readers are just as good for most cell phones. Your tightest constraint is the 3mm maximum space allocated to the mark. The rationale is that DM is more efficient in use of space and has equal or better error correction. QR was designed for Kanji characters. Data Matrix is better for alphanumeric.

For QR, you need Version 2 to keep high quality error correction and the capacity to provide for at least 15 alphanumeric characters. That provides a grid of 25x25 modules + the required 4 module perimeter of "quiet space". In this case, you are now up to 33x33 modules in the 3 mm space, so each module has to be .091mm or 0.003 inches.

With DM, ECC200 error correction (slightly better than QR), you would need a 16x16 grid +2 (total) modules for a "quiet zone" giving you an 18x18 grid. Each module would be 0.166mm or .006 inches - almost twice as large.

Whatever cell phone limit you have for detailed resolution, for 15 characters, you only need to be half as good to read the same symbol is a data matrix as you would need for a QR code.

Another consideration is the phone's resolution. I don’t know of a cell phone that can focus that small in a macro setting. I have read down to .015 inch (.38mm) modules on an iPhone 4 – but that is with perfect conditions of black-on-white. I think an extra (macro) lens will be required too.

When you mark directly on metal, you need to consider the method to use to enhance contrast for the material involved. It will require the right type of laser to maximize the contrast for any reader – cell phones are not generally capable of reading low contrast marks because the lighting isn’t optimized to enhance contrast. Reflection of the metal can cause the flash to blind the camera.
Bret daCosta
0 #4 Bret daCosta 2011-12-14 10:57
May I suggest you transition to MS TAG. A Tag can possibly be scanned at this size and offers more annalytics. The b&w format is perfect for laser etching. I have a program that can automatically generate Tags with characteristics such as unique 15 serial number. Contact:
Craig Aberle
0 #3 Craig Aberle 2011-12-14 10:41
Thanks for the input! :D
0 #2 Heinz 2011-12-14 05:15
Ii is not a Problem of the QR-Code. The Problem is the Scanner. With my LG GT540 Optimus i scan a 6mm QR-code with no problems. For 3 mm you need a better macro optic.
Oliver Warren
0 #1 Oliver Warren 2011-12-13 09:07
Wow thats a toughy.

I'm not too sure about the iphone app to scan the 3mm^2 qr code.

For the laser etching though, i've seen a company who does this for can's of coke, medicine packaging etc.

link below